Still, they could have toned it down a bit.
Going on a Chinese killing spree is kinda offensive. Especially if you are Chinese.
Look, there's a simple analogy. Watch just about any popular film from the era Mafia II is depicting: All of them are so racially insensitive, it's almost funny. But I've never heard any critic bashing those; in fact there's a lot of praise hailed from many a movie with abundant racism, pilgrim.
Sure, you can work your way around it and pretend it wasn't prominent back there, but that's sort of cheating yourself.
I wonder why this game gets so much backlash on ridiculous things like that. Same with the Italian stereotypes. Who did they talk to? I have an Italian heritage and I can tell you that no Italian person gives a smallish care about how mobsters are depicted, as it doesn't adhere with them, nor do they hold any affiliation with them. If anyone is going to be offended by a mobster stereotype, it'll be a mobster.
Things were just that bad for the minorities back then, and the game does a great job of depicting it.
If you were offended, why put yourself in a position to keep playing? You could have easily just stopped playing during one of the earlier missions when you were ordered to steal a car from a "moolie" neighborhood.