It’s likely that someone thinks it. If OP can think up that rationale and reject it, someone with less critical thinking can think it up and embrace it.

It’s not particularly useful to know if some people believe a ridiculous thing, because they almost certainly do. It’s more useful to know how widespread the thinking is and how it may influence culture. What are the consequences of this line of thought and is anyone trying to exploit it for political gain?

Without some poll or study, we can each go by personal experience. I’d wager this isn’t as commonplace as other illegitimate reasons to not like rap, include just general racism.