They're not being sincere. They're going with the most reactionary and awful take possible to get a rise while also using concern trolling and inauthentic righteousness to shield the fact that their beliefs are repugnant.
It's more common in gamer spaces, or rather, is currently. Not because of anything inherent to video games but it's important to remember that games just came out of a bullshit movement (that was totes about ethics) about a decade ago and still has a lot of gatekeeping.
It's the same way that nothing about...I dunno, anime, is intrinsically linked to lack of cleanliness, but you better believe the convention signs about please taking a bath are earned.