Does someone need permission to use a celebrity's name in a song?

So if Shia LaBeouf can prove that he doesn’t eat human flesh he could sue for slander! The song even makes clear that this isn’t fiction, as LaBeouf is described as an “actual cannibal”!

Rob Cantor Shia LaBeouf Live - Google Search

In all seriousness, clearly Shia LaBeouf didn’t mind the whole thing, but if the original song was written without his knowledge (and I believe it was, IIRC) could the fact that he’s repeatedly referred to as an ACTUAL cannibal be grounds for defamation?