If enouogh people get involved in something that there will be punishment for, it almost always makes sense to join in. Naturally, if it's something you aren't in favour of the first place, you shouldn't. If, however, it was something like (for example) a food fight, where half the cafeteria is throwing food at each other, then of course you should join in. This is because after perpetrators become numerous enough everybody in their group is punished, and you are already in that group. Your group is going to be punished regardless, you included, so you might as well have some fun with it.