I think it is just an assumption people make- that if they would not stop in a given situation, then you would not stop either- so that you stopped not only causes them to have to manouver under duress, but also questions their decision making process.
I think it is just an assumption people make- that if they would not stop in a given situation, then you would not stop either- so that you stopped not only causes them to have to manouver under duress, but also questions their decision making process.