When I was young and my parents bought their first home the police came over a few times to check on a possible burglary in progress. The reason was a malfunctioning alarm system. They came over, asked a few questions and left. Everything was very civil. After a few times we disconnected the alarm system altogether.
Later, in their new home, this happened again, this time due to an overly concerned neighbor. The last time she called the police was when my parents ordered an air conditioning system delivered. They weren't even home, and the police came and somehow managed to figure out that the workers delivering the air conditioner were not in fact burglars.
Happens all the time, really. Happens to the white, the black, the Asians and the Hispanic, and probably the Native Americans. Surely happens to the blacks more often than to everyone else, but usually everyone, including the black people, manages to sort it out with the police perfectly well.
It really takes a professor of African-American studies at Harvard University to fuck it up.
Henry Louis Gates was trying to force his own front door for some prefectly good reason, which was not, however, ovbious to a casual observer. A neighbor called in a possible burglary, which is not an unreasonable assumption to make if somebody you don't recognize is trying to break into a house. By the time the police arrived Gates and his driver already got through the back door and managed to force the front door.
At this point the cop usually says "hi, I am investigating a report on a possible burglary" or something along those lines, the owner/resident says "oh, my name is whatever and I live here", papers are checked if the police finds it necessary, both say "oops" and the cop leaves.
"I live here" is the right answer. "Why, because I am a black man in America" is the wrong answer, and so is "you have no idea who you are messing with". He is not messing with anyone, he is doing his job, which, among other things, includes investigating burglaries in progress. Whether or not the neighbor would have called it in if those were two white men forcing the front door is something you can speculate about in your African-American studies class, but for the sake of all our front doors I certainly hope she would've.
You especially don't follow the officer outside and keep screaming at them. This is what gets you arrested for being disorderly, which is exactly what happened to Gates.
Now the incident has made the national news, the mayor has apologized, the charges have been dropped, the officer has refused to apologize and he-who-cannot-be-called-chimp-in-chief has also criticized the police.
One thing is not entirely clear: what does Gates want the police to do if there is an actual burglary in progress? Come there, see if the burglars are African-American and decide that asking them about anything would be an undue act of racial profiling?