[frumper]

Not talking to people is rarely the solution for resolving conflicts. You also have made some assumptions that someone pissing you off is now a shitty person. You've also set an unreasonably high bar of totally reasonable. I think most people are mostly reasonable about their kids. If you start off with "Hi, your shitty kid is pissing me off" then sure, you're not likely to get far, but if you explain legitimate concerns then most people are likely to respond reasonably.