I'm not saying that every instance or even the majority of instances are a one to one substitution.
But what I think does happen, is some people see a black man "act up" and immediately label that person a thug regardless of if the person is even remotely "thuggish." Richard Sherman went to Stanford. Now, Jaric may not have his fingers on the pulse of the streets, but I don't recall Dre or Biggie rapping about going to history class at Ivy League schools. Maybe those tracks never made it out of the studio.
I'm normally the first to roll my eyes at "code word" accusations but ask yourself this: if Richard Sherman looked like Tom Brady, do you think anyone would accuse him of being a "thug?"