I can see it's an old thread but recently looking at this subject I thought I would post some of my thoughts
Who ever these sons of God where their offspring were giants and not long after violence was rife.
It doesn't say they had superpowers or futuristic intelligence but seem to be tall strong and mighty
(If the sons of God were angels at the time as they were presenting themselves before God then why where they not referenced as angels and if they were fallen angels why were they then referenced to as sons of God, they must be something else.
On at least 2 occasions God has bound fallen angels.)
when the Sons of God saw the daughters of men - my spirit shall not always strive with man....God judged man not Nephilim or giants of fallen angels.
Angels can take human form but cannot marry or procreate
Demon's did not take on human for, cannot procreate also unless for deception
Angels do not love - they worship God but doesn't say they love. Satan and his demon's will worship God but not love him but will show true benevolence. Did these sons of God love the women they were marrying?
Why would a demonic spirit marry why not decieive the women to say it isn't needed?
Angels were never referred to as sons of God.
What happened after flood how did they come back?
In both instances where the sons of God presented themselves before him (including story of Job) it doesn't state that they were before God in heaven! It could have been before God on earth.
It's a thought provoking concept who/what are the sons of God