I guess as the ideas of what is socially appropriate and what is not changes, it's easy to associate that with Christian truths. If they believe that people were more spiritual back then--which may be the case--that might influence it, too. I'd call that the post hoc ergo propter hoc fallacy.questdriven:
Yes, interesting.
Anyway I'm sure that there are many young Christians from a Fundamentalist background who also happen to like Christian heavy metal and hard rock.
They ought not to be seen as contradictory associations, I don't think.
What God does by His Spirit through faith in the Lord Jesus is change us from the inside, as we seek to serve our generation, not necessarily the culture of two or three generations back.
Blessings.
Post hoc ergo propter hoc: the logical fallacy that because something happens after something else, then the first event must be the cause of the second.
~Wiktionary
So when culture changes, and they see people getting away from God, they assume that the culture change must be the cause of it.