They come to snuff the Rooster

so, if you spit on a guy, you're going to get punched. everyone knows this. if you've ever gotten spat on, you know all about this. i guess it's just cultural, but when someone intentionally spits on you it makes you want to hurt them really bad.
of course, there are laws against hurting people really bad, presumably even if they spit on you.

so what do you think? if everyone knows that when X happens, people respond by doing Y, and everyone agrees that when X happens to them, they at least -really- want to do Y, does it make sense for a legal system to overrule that?