If someone broke my car window and was pulling me out, I would definitely consider that a level of force on their part that could be met with lethal force on my part. The law would be on my side too (at least where I live). If their hands were on me, dragging me out, I would respond accordingly to save my life - and it sure as heck wouldn't be with pepper spray or a stun gun at that point. But some people, due to where they choose to live and the government there, do not have viable options like those of us in other states/countries do. So you have to find out what your personal options are and work within that, or move to a place that allows you more effective options.

The best defense, of course, is to avoid getting into the situation in the first place. Stay away from rioting mobs (duh!)

This video gives a very good demonstration of the effectiveness of pepper spray (on non-violent protesters):

http://www.youtube.com/watch?v=6AdDLhPwpp4