I disagree. Blocking vehicles as a pedestrian is a nuisance regardless of motivation and ideology, but no one deserves to be run over unless they are presenting a threat that legally and morally justifies lethal force.
I haven't had to deal with this yet, but wouldn't moving slowly just push someone out of the way? If they are lying down I suppose that'll be a problem, but at least they can't spray-paint you.
Running over a protester isn't entirely comparable.