It's because they always have to morally grandstand about how they're
such a good person for calling out the
evils of racism from a game that most people wouldn't seriously care about and would only play it to spite pricks like this.
Honestly, he would have been better off just laughing at Ethnic Cleansing rather than getting horrified.
It's the same mistake Extra Credits made when it came to the game Hatred. You come off as a faggot because you can't accept that humans are capable of cruelty, all because you took a game about killing everyone seriously. You decided to be a moral arbitrator of what is right and wrong because you want the whole world to be one big day care.
It's insanely pathetic.
https://youtube.com/watch?v=s6xQlnzffRg
Hell, I'll give Ethnic Cleansing this. At least it's honest about what it's about, as opposed to so many other games, whether it's indie or triple-A. They'll go out of their way to push "games" that actively tell you that it's okay for white people to go extinct and everyone should become super gay.
And more often than not, those very "games" tend to have the support of those who claim to be the least racist.