Yea, you have to grab the first offender's arm and say loudly and sternly-"Do not hit/kick me or I will hit back." This generally send a message to him and his friends, that unruly behavior is not tolerated.
The worse are stupid teenagers and/or adults that act like children. You have to watch your partner's back, like the real world, do interference/blocker That's when you really play in character of a Sandtrooper.
It is unfortunate, but a necessity for our safety, that you may have to act like a bodyguard and man handle individuals. From experience, having a handler that know how to deal with crowds is a must. I had an unqualified handler, and subsequently an individual walked up punched my helmet. My helmet twisted around, while the guy ran off laughing. And my handler stood their like an idiot. If it weren't for the children I was posing pictures with, things would have been very different for laughing boy- 19-20 year old. I went and took a break right after to cool off.