DiDi — this is an exceptionally bad idea for a number of reasons. The first is that you are advocating violence which begets more violence and is rarely successful. Nonviolent actions work, mini-revolutions just get crushed.
The second is that it plays into the hands of those who would paint BLM (and black people in general) as violent, lawless and angry.
The third is the one you point out about getting killed at worse, or imprisoned at best.
The fourth, and perhaps most important, is that you’re not clear about what you are for — it’s all anger and what you’re against. Are you for respectful treatment governed by law, including applied to the police? De-escalation rather than beat-downs? Surely you can see that punching cops is the opposite of that. If you clarify what you actually stand for — beyond Mel Gibson-style violent fantasy — you will probably find that punching cops is not the way to get there.
More Ghandi, less thuggery.