What's the deal with Genesis 6:1-7

I shall quote this article at length because it is a helpful guide in helping one understand the strangest passage in the Bible (I don't expect anyone to read it all, but for the very curious people it might do them some good):

"The first matter and indeed the main thing about which there has been the greatest amount of discussion has to do with the meaning of verses 1 and 2. What is meant by the phrase "Sons of God"? To whom is this referring? Likewise, who are the "daughters of men"? What is the reference for this phrase?
Well, as you can imagine, bible scholars over the years have speculated a great deal about these things and a number of proposals for how to understand these phrases have been put forward. However, the vast majority of scholars, as far as I can tell, end up taking one of two main positions, which we will spend the next few minutes considering.
One viewpoint takes the position that "Sons of God" is a reference to angelic beings that entered into God's creation and engaged in sexual relations with human beings - with the women who are spoken of in verse 1 as rapidly multiplying across the face of the earth, as the human race expands itself. Some of the arguments that are marshaled to support this position are:

1) The phrase "sons of God" while not appearing anywhere else in Moses' writings - and so difficult to be sure of - does nevertheless appear in other places in the Old Testament - like Job - where the context makes it clear that the phrase is a reference to angelic beings.
2) The co-habitation and co-mingling of angelic and human beings does seem to fit with a
developing plot line that shows the downward progression of sin. So, for example, sin begins with the woman and the man in the garden, starting internally with certain thought patterns which then lead to some external actions that are sinful. It then manifests itself in the man and woman's relationship with each other. It then manifests itself in a pronounced curse which affects the creation itself and all future humanity. We then see it in the story of Cain and Abel - with Abel being murdered by his brother. We next see it in the genealogy of the descendants of Cain, and especially in Lamech who is a violent murderer who boasts to his wives about his deeds. And then, in this viewpoint at least, the climax of all this is when the angelic beings come and mix with the human race, spreading the corruption of sin to cosmic, supernatural dimensions.
3) In keeping with all of that - this sort of radical, bizarre evil would help explain why God's response to it - in the form of an all-devastating flood - seems to be equally radical.
4) The view that these are angelic beings would seem to be supported by other passages in the New Testament which are possibly referring to this very event - or at least to something like it. (Read 1 Peter 3:18-19; 2 Peter 2:4-10a; Jude 6-7). It is possible that all these verses have in view the events of Genesis 6 - seen from this certain perspective.
5) As one scholar seems to suggest (Kidner), this perspective could be seen as a second attempt on the part of angelic beings to thwart the purposes of God. The first attempt was what we have already seen in Genesis 3 when Satan, in the form of the serpent, comes to the woman and tempts her to sin. After those events, in which she was promised she would become "like gods” she and her husband are cast out of the garden so that they might not eat of the tree of life in their sinful condition and thus gain immortality in their fallen state. As this one scholar suggests, in Genesis 6 we have not just one but a number of angelic beings again coming to not one but many "daughters" of men and trying to achieve for them both power and possibly the immortality that had been denied them by means of this unholy union between humanity and angels.
6) Finally, the view that these were angels is possibly linked to the account here of the Nephilim - mighty warriors. In other words, even though it is not specifically stated, it might be taken as implied that the Nephilim are the sort of "hybrid" offsping of the union between women and angels. However, this is far from obvious in the passage, but I will say more about that in a moment.

At any rate, that is one view that many scholars maintain as the most likely reading of these verses. The other view that is held by many scholars is that the phrase "Sons of God" refers not to angelic beings but simply to men who were born in the godly line of Seth.
Correspondingly, in this view the "daughters of men" are women who belong to the ungodly line - the descendants of Cain. And so, this view is simply saying that what began to happen was a mixing of the two lines - the godly with the ungodly. This greatly angered God, and then we all know what happened after that. Now, some of the main arguments in favor of this view are:
1) It does seem to fit better with the immediate context of the last couple of chapters. In Genesis 3:15, as we have already seen, contained in the curses pronounced against the woman was the promise that the offspring of the woman would crush the offspring of the serpent. And so there is forecast there the development of two lines of humanity. What we see next in Genesis takes this further with chapter 4 showing us the Cain and Abel conflict - which was simply the seed of the serpent (Cain) making a futile, but pre-emptive strike against the seed of the woman (Abel). We then see the story of Cain and his descendants and the development of that line, followed by the genealogy of Seth with his descendants the development of the other line. To then see chapter 6 as this event where the descendants of Seth were being lured away by lust and sensuality into illicit marriages with the descendants of Cain would seem to be flow quite well with the immediate context.
2) To regard the "Sons of God" as angels does, it could be argued, seem like something of an intrusion into the text. We're not really talking about angels here; that's not the subject of concern and then, all of the sudden, there they are. It does seem a little surprising but then it must be said that the same thing could be said of the events in Genesis 3. There you are, the story going along just fine about creation when suddenly, out of the blue, there is a talking snake.
3) The view that "sons of God' is referring to the descendants of Seth and not to angelic beings also seems to fit better with what follows in Genesis 6:3. In verse 3 you have God saying that he is not going to put up with the sinfulness of man forever. Indeed, God even puts a time limit on the whole thing saying that the clock is running and that after 120 years, he will carry out his judgment against humanity. The important thing' about all this for the point at hand is simply that if verses 1 and 2 were talking about a co-mingling of angelic beings and humanity, then you would think that the words here would include judgments against angels as well as humans, for they were equally guilty. But no word is mentioned. When you compare this to Genesis 3 you see that God pronounces curses and judgment against both the humans and against the serpent, or Satan. At the same time, while no word of judgment is mentioned here - if you take into account the other passages that we just read from the New Testament as

referring to these events - then in those passages you do find promised words of judgment that awaits angelic beings.
4) This view is also possibly supported by the fact that the "sons of God" here - whoever they are - are described as "taking wives" to themselves - language which is almost always used to refer to the act of marriage and thus seems to fit more naturally with what humans do, not angels. The text that is usually brought in to support this point is Matthew 22:29-30. This text, understood one way, could be read as rendering the marriage of angels outside the realm of possibility but then, read another way, does not necessarily exclude that possibility at all. So, it's not a strong point, but it is a point nonetheless.
5) Finally, in support of this view a scholar named Currid says that a better translation of Genesis 4:26 would make the meaning of this passage more obvious. In short, he makes the case that instead of saying that "people began to call upon the name of the Lord" a better translation is "men began to be called by the name Yahw*' or, in other words, men began to be called by the name of God. If that is correct, then for Genesis 6:2 to come along later and refer to actions taken by "sons of God" then it would seem to be a more obvious linguistic connection. And so, those two views - that "sons of God" refers to angelic beings OR that it refers to the descendants of Seth - those are the main ones being offered and defended. But the reality is that there are problems that arise no matter which one you take.
As far as the "angelic" view is concerned, it does seem to interrupt the flow of the story as we see the developing account of the line of Cain vs the line of Seth. And yet, while it seems to interrupt that flow, it seems to enhance another one - the downward progression of sin. The angelic view also, as we have seen, leaves us wondering why no immediate word of judgment is pronounced against the angels for their part in the sin. And, further, it seems to contradict Jesus words about angels in Matthew 22.
As far as the "two lines of humanity" view is concerned, you have the same problem as outlined above - it flows well with one line of development, but seems to interrupt another one.
Another difficulty is outlined by a guy named Motyer who says, "the mere mingling of some godly with some ungodly humans is hardly the sort of climactic sin which Gen 6 appears to require by its place in the narrative." To that, Motyer adds this comment: "there is no reason why a mixed human marriage should produce the sort of offspring that Genesis 6:4 implies (although, it must be said, the text is not necessarily implying this and, in fact, may be trying to make the exact opposite point - that the Nephilim were not at all superhuman but were simply extraordinary humans). One final problem with this view is that it would seem to present a different picture than what is suggested by the New Testament passages we read earlier."