Curiosity question about the truck driver running into a Pro-choice crowd yesterday.

This should work out just fine, especially in the kind of states that have 'stand your ground ' laws.

Running down protesters is legal now?

I think that gunfire for self preservation is an option in the case of note.

Right before and in the middle of him running people over, yes. After he already hit them and was "fleeing", then no. Caveat to that is if he is fleeing in the direction of another crowd, then one can argue he is still an imminent threat and it would be legal. Generally, immediately before and during the attack would be legal self defense, after the attack has ceased would not be.