Then why did you call the wickedness of marrying those they should not have as "evangelism"?That is why the deluge occurred. Haven't you ever read the Bible?
The "sons of GOD" in the verse are the bad guys, doing something they should not be doing.
By trying to force the verse to say "the line of Seth" (which it does not) forces the line of Seth to be the wicked ones, not the Godly ones.
That obliterates the theory that the line of Seth was Godly while the line of Cain was wicked.