"can talk back more aggressively than the others" - opinion.
"only race that seems have" - opinion.
"If I were a police officer" - I'm glad you aren't.
"I'd probably end up fining more black people" - clearly.
"My guess is that whatever gives black people a 'black accent' or voice is also what's responsible for the fining and bad subculture." - history is recorded so you don't have to guess. To fine someone for an accent is discrimination and illegal.
"they wouldn't be fined as much" - evidence please.
"I would also guess ..." - guessing is the basis of discrimination.
Rather than guess, I recommend researching for facts, ask why, make sure your facts are right, repeat. Bonus points for optimism, empathy, and assuming others want the same from life as you.