Earlier quoted context omitted.
Gender is entirely a social construct very loosely tied to biology but not at all determined by it. I personally think the same thing is probably true of sexual orientation (which really is sexual attraction to gender not necessarily the same sex ). I would add that many anthropologists don't think people are born with a gender.
Gender is entirely a social construct very loosely tied to biology but not at all determined by it. This doesn't sound plausible. [tl;dr: If evolution didn't build in a powerful urge to make our gender behavior match our reproductive sex, then it made a huge error and missed a very easy and effective optimization.] It may be the case that gender could be very loosely tied to biology in a philosophical or theoretical…
That's not how evolution works! Evolution works at the level of genes, and not individuals. It's easy to construct a model where a 10% gay population ends up being overall better for a population. Consider this made-up hypothesis: gay people are better at caregiving than non-gay people, so a population with gay people ends up with healthier adults who are able to have more, and healthier, children. For this scenario, gayness won't be "optimized" away because that leads to worse reproductive success for the population of genes involved. Nor is the presence of gay individuals "damage", because the result is an evolutionarily better population than one without gay individuals.
As another example, why does Down's syndrome exist? By your logic, shouldn't evolution have optimized that case away? That it hasn't means that changing how the 21st chromosome works is much harder than the impact of having a 1:733 failure rate. Why do you assume that any genetic component to being gay would be easy to change, without having negative consequences elsewhere in the population?
So your error is the belief that evolution emphasizes the reproductive success of individuals, when it deals instead with the reproductive success of genes. Some individuals don't need to reproduce so long as the overall gene population reproduces itself.
BTW, 100 years ago, pink was a boy's color, and young boys wore dresses too. Quoting from http://www.smithsonianmag.com/arts-culture/When-Did-Girls-St... "yet social convention of 1884, when FDR was photographed at age 2 1/2, dictated that boys wore dresses until age 6 or 7, also the time of their first haircut. Franklin’s outfit was considered gender-neutral."