They absolutely are, they're both watched by thousands of people, and influence thousands of people. The only difference here is that gaming culture is already toxic towards woman, so who gives a fuck if people exclude them more, right? That's why no one bats an eyelash.
Furthermore, that still doesn't change that it's sexist. It's his prerogative who he has as guests on his stream, but by the same token, everyone else can still call out his decisions for what they are. Sexist. It doesn't matter what his reason is, he is still discriminating women based of their gender. Which is the definition of the damn word.
It's as if you think that just because he can get away with it due to the sexist gaming culture, that it suddenly makes the decision fine? That doesn't negate the fact it's a sexist decision. Nor does it stop people from criticising it.