"the "acceptance" of homosexuality is a relatively new phenomenon"
So is:
1) human flight
2) antibiotics
3) interracial marriage
4) freedom from slavery
5) the fight against racism
6) capitalism (by your 4000 year scale)
7) spongebob
There's more to the bible than homosexuality being a sin, and that's what's really defined our civilization. Homosexuality affects a very small percentage of our population, and many of its members are that way for a variety of reasons.
Regarding "last gasp of a dying culture": I'd say that allowing abortions would be on that list. Another thing would be any kind of tyrany, or corruption in the government. Homosexual marriage is the last gasp of a dying custom, and I'll grant that there are serious issues there to contend with. It might be better for gay activists if they stuck to "civil unions".
1) human flight
A scientific achievment, not a cultural shift.
2) antibiotics
A scientific achievment, not a cultural shift.
3) interracial marriage
A cultural shift. And not necessarily a good one.
4) freedom from slavery
A cultural shift that brought us INTO alignment with God's wishes, not one that propelled us farther away.
5) the fight against racism
A cultural shift that has been marred by repeated abuses on the "victim" side.
6) capitalism (by your 4000 year scale)
You're daft. Capitalism -- in one form or another -- has existed since the dawn of time. True, it required an Industrial Revolution to give it its present incarnation, but people have been buying and selling at a profit for eons.
7) spongebob
A cultural mistake.
By the way, the Bible never condemned human flight, antibiotics, capitalism, or Sponge Bob (sadly). On the other hand, it does criticize bigotry and the abuses of slavery (although it is oddly ambivalent on the actual institution).
Your moral equivalency argument doesn't wash.