I wish it were as simple as them being gay. But I think it more comes from how society on the left is being taught that straight male desire is inherently wrong. A man desiring a woman, wanting to find her sexy - that's gross MRA stuff that leads to rape culture. It's been pointed out before, but SJW culture is a very puritan culture that pretends to be sex-positive but really isn't. It's trying to be a bit more turnabout is fair play - women ogling men is OK now while men are shamed for doing so - but at the end of the day it really does come down pretty heavily against sex in general, straight sex in particular.
So they complain and attack all these things, and these men learn that their desires are wrong and bad. So if they find a woman in a game sexy, that means there's something wrong with her being that way, because they're meant to be good people who respect women. They get in trouble, or have seen men get in trouble, for merely describing a female character as attractive, for talking to a woman in a bar, for even looking at a woman in a way that made her uncomfortable.
So I think some of it is virtue-signalling, the whole 'ma'am may I please have some coochie?' sentiment where if they show how good they are maybe these women will deign to treat them well. And I think some of it is the product of men trying to do the right thing, not realising the right thing is being changed constantly so they'll likely not keep up, nor are they meant to.
And some of it - well, some of it is what leads to secret porn addictions and male feminists being accused of abuse and all the rest of it. Because their desires are bad and wrong and shameful and private, and repressing that in the era of the internet seems to make people fucked up in different ways than it used to.