It does seem a little unfair to physically hit someone for something that happened in a dream!
My sister's ex husband had a dream that someone was invading the house and threatening the family, and he woke up swinging his fist. It took him a second or two to realize it was my sister there and not an evil attacker. Luckily he realized it in time, but it's scary. My boyfriend is very strong and could easily overpower me, and he sleeps very soundly. If he woke with some sort of a fear / attack thing strong in his mind, I would have to hope he snapped out of it really quickly.