Agreed. Whenever a radical leftist claims they are believers of science, ask them how many genders there are.
Right?
My opinion might differ from yours, in this regard. Remember, I'm not an idealist when I say any of this, so I'm not approaching this from an SJW perspective.
I would argue that there are two sexes, but that "gender" as defined by the left is just a set of cultural symbols, like "boys wear blue, and girls wear pink". I think the right often mishandles this issue, in attempting to avoid the lunacy regarding PC culture and transgender issues.
It's important to distinguish between actual "transgendered" people in the traditional sense, and SJW nonsense. Many if not most transgendered people have what should be called "sex dysphoria", where even if they were on a deserted island, they'd feel as if they were born in the wrong skin. I've known a few people like this. They're not political, and suffer from what they would describe as a severe form of mental anguish. For them, embracing the opposite gender (clothing, mannerisms etc) or getting surgery is a coping mechanism for their very real mental discomfort. These people are ironically very conscious of gender, and want to "pass" as male or female so that they are perceived the way they feel. I have OCD, and while I wouldn't speak for anyone else, I've been told that it's very similar to my experiences of intrusive "ego dystonic" thoughts.
Then, there are the neo-hippy SJW cretins exploiting transgendered people. These are the parasites who want you to memorize a laundry list of pronouns, in the name of justice. While I agree with those of them who argue that gender is a construct, they fail to understand that most of the population doesn't distinguish between gender and sex. When people use pronouns, most of them are referring to sex, and not gender.
So, when you see a guy dressed as a woman, you might think, "That's a He. Don't take them home, dude." That's fine. However, I think that if you're a nice guy, and don't want to hurt people unnecessarily, it's a tactful thing to accommodate people clearly trying to appear as a man or woman, to help them deal with their mental anguish.
There are a select few who attempt to deal with sex dysphoria by attempting to accept the way they were born, and describing themselves as "gender neutral". If that works for you, great. However, I honestly see it as accommodating mental anguish, the way we'd be expected to install ramps for people in wheel chairs. If there's a disconnect between your sex and your cognition, you have a problem.
This has been entirely mishandled by SJW's advocating on behalf of transgendered people. There has been very little attempt to educate people regarding the problems some people face, in dealing with sex related cognition. The issue of whether or not beards are feminine, men can wear dresses etc. is just cultural nonsense. It should be irrelevant to what has become the politicization of an affliction.