The Plumbing Forum is a different thing, I think been dumb is part of the requirements of a plumber so it would be pointless having it has a rating, it simply goes without saying.
haha... Poor plumbers.
In the real world you don't see people joining into a conversation of strangers and telling one of them what they said was dumb then walking off without so much as any explanation, so why do it on a forum, the reaction and confusion is just the same and any recipient probably would want to know why it was said/given.
I wouldn't joining into a conversation with strangers and say that they were dumb.... If I thought it I would just walk off.
A conversation with friends, then that's a different matter. They would get a lot worse than being called dumb..