I have long wondered what the connection was between the New Atheist ideology and their almost universal support for same-sex marriage in particular and, in general, their impatience with any position that views heterosexuality as normative.
There is a clear symmetry in biology between male and female. If anything goes together biologically, they do. And biology points to this in the strongest way it possibly could.
Now I don't believe that normativity has any necessary connection to biology or any other science. But the interesting thing is that they do. Or at least most of them.
You have a minority of New Atheists who take their materialist determinism to its logical conclusion, who claim that there is no free will and that consequently deny human responsibility (e.g., Alex Rosenberg, Sam Harris, etc.), but most of the New Atheists don't take their own scientistic beliefs to their logical conclusion and claim instead that morality somehow comes out of biological states.
Let's state that more strongly (because they do): Biology produces morality.
They don't have any good reason for believing this, mind you. When you ask them, they just produce some dreamy science mythology on the order of: "Well you see man in his early development began his development thus, and then he continued to develop this way and that, and then he became a moral creature--the "then" here being a conjunction masquerading as a logical therefore. They believe that somehow putting the arrival of the moral sense in a temporal sequence had some logically explanatory force, which, of course, it does not.
But for these latter atheists biology is the very thing that produced the normative. They believe this on every normative issue. Biology produces morality on ever issue ...
Except one: human sexuality.
When it comes to human sexuality, where the normatively-charged biology clearly points to the male and the female as being complementary, all of a sudden they mysteriously abandon the belief in the normative nature of biology.
Biology determines morality on every issue but this one. Morality arises from biology for everything but the reproductive organs which, as I have pointed out before, are no longer for reproduction because (and here they have a massive memory lapse about everything they have said about morality before this point) nothing is for anything.
Biology produces morality. Remember that. Except when we talk about sex. Then we need to completely forget it and pretend we never said it.
To say, as traditional peoples--including homosexuals themselves up until recent times--that homosexuality is "not natural" is now a laughable thing to say. It is as if biology were, oh, I don't know, natural.