That is why we have GMs to look at chat logs. Don't respond and kick him if he's being confrontational. Telling someone their gear isn't good enough for the content you are doing is okay, it's how you say it that is important. If they lash out because you told them politely you have nothing to worry about. I really am looking at your objection to the rules as hey I want to be able to tell this person they are a moron. It's hard to see the problem people have with this because the answer is simple just be polite and if that doesn't work kick the offender or leave.