This idea, that gender is entirely linked to biological sex and that how children are socialized has little to no impact, is completely misguided and ignorant.
Of course, but to make the opposite mistake (which you seem to be doing here) is just as misguided and ignorant. There are strong biological differences between men and women. Yes, you can find examples that go against this fact, but that doesn't disprove the trend. And yes, environment plays a big part in how we all turn out, but so does biology. It isn't a small part by any means. If it was small, those boys that were raised as normal, hetero boys but turned into giant flaming queens when they turned 24 wouldn't exist. Their environment didn't make them gay, it was already in them when they were born. Biology.
