Youd have to ask the rappers who said it.
Cultural appropriation is the adoption or use of elements of one culture by members of a different culture.
culture vulture
Someone who steals traits, language and/or fashion from another ethnic OR social group in order to create their own identity.
If you think someone being "half black" means they cant be a culture vulture then

houston has a culture, Ny has a culture, L.A has a culture, Chicago has a culture, etc.
Is it because he sounds like a white man in interviews and blacks himself up in certain settings?
Could it be that he repped Houston harder than his own city, now everything is conveniently about toronto?
Could it be that he repped houston but didnt really working with Houston artists?
Could it be that he hops on the wave of up and comers?
I dunno, you gotta ask the guys who said it.