The view that there are only two sexes is completely mainstream in biology:

https://www.wsj.com/articles/a-biologist-explains-why-sex-is...

> That is absolutely a hateful, illegitimate opinion.

An opinion can be true or false. That it is allegedly motivated by hate is a baseless accusation. It can be claimed about anything. "Don't believe God exist? Must be hate speech! Punish him." This all happened before.