Of course you can’t force people to change their views, but you can still do some things to make incidents like this less likely:
- Stricter punishments
- Quota for policeman (don’t know if something like this already exists), more Asian/black/Latino/female policeman (they seem to be less prone to racism)
- When a policeman has shown certain „tendencies“ in the past, then maybe „letting it slide“ isn’t the best option. In this case it was pretty clear that this guy „wasn’t right“
I am sure there are tons of other options for reforms, but of course the most important thing would be to reduce/eliminate institutional racism in general. Non-white people have less political opportunities (not only because they are poorer), so „their“ candidates have less chance of getting elected, which leads to reforms becoming less likely ... (as you know there is a lot of money involved in American politics, so the poorer you are, the less influence you will have on politicians).
It also has to be said that:
a) Even under Obama not much changed, which might indicate how „stubborn“ some people in power are when it comes to changing things.
b) Some control mechanism have already been installed, for example body-cams, so it is also wrong to say that nothing can be done.