5) Is it okay to invalidate someone's gender identity? Wouldn't invalidating someone's gender identity be lgbtphobic? If no, can you explain why?

I have nothing meaningful to add to what the wonderful people here have already said in response to this post (with a lot more patience than it perhaps deserves, because I find it hard to believe this post is in good faith when the sub rules clearly state that this is not a debate sub), but I would like to counter this question of yours with another question.

Why is it okay to invalidate women's lived experiences, our biological experiences? Historically women have been oppressed because of things like our periods and our ability to bear children, and we still are today. It had nothing to do with "identity" then and it has nothing to do with "identity" now. Women are a huge group with a vast array of personality differences, likes, dislikes, etc., and here you are shoehorning us into a "gender identity" riddled with stereotypes. What we have in common is our biology.

And before you come at me with "sex is on a spectrum, it's sCiEnCe," I want to give you a little lesson on the peer review process and scientific consensus. Opinion pieces in magazines are not peer reviewed. They may seem to be written based on current scientific findings, but the very fact that they are opinion means they have no basis in the scientific method. That being said, peer review is imperfect because it is done by humans, all of whom have biases and opinions. That's the reason the scientific community needs to come to a consensus on any given topic (which can only happen with extensive peer review of myriad studies, in order to remove the bias). Consensus indicates that most scientists who are subject-matter experts agree with a specific outcome/observation based on the science/research that has been conducted and presented. Take climate change: though there are a few (loud) dissenters, the scientific community has been at consensus (something like 97%, if memory serves) about anthropogenic climate change for years. By the way: the experience a scientist has with the subject is important in consensus. It doesn't matter much if a particle physicist disagrees with climate change. So it doesn't much matter if a psychologist disagrees with the concept of binary sex (because that psychologist was not trained in biology.)

Scientists are NOT at consensus with "sex is a spectrum." Plenty of scientists are trying to clarify this point of view and do not find that it has any scientific merit. While secondary sex characteristics are quite vast and varied, the human body is only capable of producing one of two gametes capable of creating a zygote. The presence of genetic disorders does not constitute a third sex, because these disorders do not produce a third gamete. The presence or absence of various secondary sex characteristics does not constitute a third sex because, again, these individuals do not produce a third gamete. The fact that some people are infertile again does not constitute a third sex, nor does it suddenly imply that they are "less of" a woman or a man. Their bodies are still blueprinted by genetics to produce one of two gametes, the fact that they cannot doesn't suddenly mean "sex is a spectrum," and I think it's cruel to insinuate that they aren't as "male" or as "female" as their fertile counterparts (i.e. that they fall somewhere on the middle of the spectrum) just because something went physiologically wonky with their reproduction.

Find me a peer reviewed paper (actually, I would like several, because sometimes duds make it past the peer review process and it's only when another group of scientists tries to replicate the results that people realize the first paper had no merit) showing evidence that there is a third HUMAN gamete capable of either being fertilized by sperm, or fertilizing an egg, and I will reconsider my position that sex is not a spectrum. (Some species actually do have more than two sexes. Look up slime molds.)

Finally, I want to state that I am not a biological essentialist. The human body is sexually dimorphic (male and female) but that does not mean that one sex is better than the other, or that either sex should behave in a certain way. Sex stereotypes (e.g. dresses are for women, men like cars, women are bad at math) have never made sense to me, because people are way more complicated than that. That being said, because women have faced oppression for so long, we deserve separate, safe spaces. Similarly, people with genetic disorders and fertility issues deserve our respect and have a right to privacy, I think it's time we stop dragging them into this debate as proof of false science, don't you?