I was told sit still in the car, don't move, don't move hands. Pay extremely attention to the police, otherwise you may get shoot. I told my friends and family exactly the same thing. The blacks have much more chance to be shoot, it's well known.
BTW, I live in the most developed and safest high tech place in US.
There are Israelis, Kurds in Iran. I didn't hear they are discriminated. This isolate issue should be fixed if it's true, but basically it happens everywhere.
Regarding more broadly issues, personally, I suggest Iran to adapt a reform and opening up policy, like China did in past 40 years. But it's up to Iranians and international environment.