Don't call people idiots. It's an insult based on opinion - much like wanker and jackass and all those other kind of things. Of course, it can be used lightheartedly and between friends without any real offence being caused towards the person it's aimed at, but the point is we don't want other people going along, seeing it and then doing the same in a much less jokey way later on.
On a sidenote, for all you people who can't be bothered figuring out how to get the ^ above the u in Kawaii Ryűkishi, just type this: Kawaii Ryu</>ukishi. With two u's. It'll automatically change to Kawaii Ryűkishi. Nifty.
