Even without self-driving cars, an "attacker" can go into a theater and yell "fire" and cause a stampede.
They can get a high-viz vest and clipboard, and stand in intersections directing cars to take detours they don't need and holding up traffic.
My point here is that society has a lot of trust baked in. We trust people don't just yell "fire" without reason. Just because it's FSD cars doesn't mean people will start broadcasting the equivalent of "fire" constantly. It's already easy to cause accidents.
