It's more than showing the character, it's the actions that we see as well.
SPOILER ALERT.....
When Sam Rockwell's character beats up the real estate agent and throws him out the 2nd floor window, then as he exits he punches the secretary and walks back to the station as if nothing had happened. And absolutely nothing happens to him?! He doesn't get arrested or fired for that?!
Then when Frances McDormand fire bombs the police station(a very absurd moment in the movie) she's not even brought in as a suspect, because Peter Dinklage's alibi is apparently very believable?! Who else would have done such a thing?! Not only the police racist in this movie, they are incredibly incompetent.
And we as audience members are supposed to take this seriously? Because the filmmakers do not try to portray these moments as comical.