O please. Get a grip. You'll get yourself shot. Or you'll shot a cop, and give an excuse for even more violence and state repression. Individuals can't fight their way out of repressive regimes.
Get a camera, set it to record to a remote location, preferable a data center in another country. What we really need are tech volunteers to start setting up these types of digital cameras in ethnic neighborhoods to document what is happening.
Feeling uncomfortable is not irrational. Being anxious to take public transit, out of fear of encountering a mentally ill person that might act out violently, is actually a common fear. There is a stigma about talking about this. Careful about finding yourself in an echo chamber.