Being a wigger rapper (This shit is fucking old but tbh this sentiment never really went away from black communities. It's just more hidden.
Being a fake rapper (The infamous

tweet comes to mind as Calli clearly isn't on the "inside" of the hardcore rapper world. Also the fact that she blew up when she debuted means she didn't ascend to "true artist" fame by hawking her soundcloud mixtapes on the streets of Shibuya like the REAL rappers)
Being a white rapper doing japanese raps (This isn't so much about rapping but Japan's cultural hatred of foreigners runs deep, so having whitey borrow some culture rubs some japs the wrong way)
Being a bad rapper. (This is stupid to talk about because art is art. It doesn't matter how technically skilled you are if the music doesn't appeal. Calli may or may not be as good at rapping as other people but people obviously like it for a reason.)
DEMONDICE SOLD OUT YOU GUYS (This one isn't really used much these days since Calli has proven that she still releases stuff under her roommate's name but a decent chunk of her old fanbase were really unhappy and thought she was abandoning her roots for profit)
Backstabbed by friends. (It's been a while since she ever talked about it but a lot of people in the underground rap scene dunked on Calli and hated her when she blew up in popularity. It got so bad that some friends and respected peers she admired also shat on her probably for one of the other reasons listed above. Those people she cut ties with are probably spreading shit about her to this day if they haven't moved on.)
Cuckbeats. (We all joke about it but there actually was a significantly loud minority that wanted their "dad" to stop hanging around her bros. Gets weirder the more you think about it)