"Would it be OK for someone sent on a mission with a wig to try to shove a fake award from a fake corporation into Obama's face when he gets out of a car?"

That's an interesting question. In the UK our politicians don't tend to be so quarantined from the 'general public'. In the course of their campaign rounds if someone present decided to ask a politician a potentially awkward question or perhaps make a political point by placing them in some mildly embarrassing position (say by offering them a plastic trophy or something) they could do so without necessarily expecting to be physically assaulted and trodden upon.