It's definitely not entrapment. That's when the police lure you into committing a crime just they can arrest you.

I have heard that blocking in someone's car can be considered kidnapping, if they are trapping you inside.

The main thing to bear in mind, though, is that it is only a crime if the system allows it to be one. In most cases, the system will side with the protestors over you if you do anything to disperse them.

I personally consider it tantamount to a violent threat (especially after several motorists were dragged from their vehicles and beaten by "protestors" during the Summer of Love) and people are morally justified to do what they need to get to safety.