Ryoko, I think your line is a logical fallacy. You are looking at the act and thinking, that's a bad thing, therefore person who did the bad thing must be mad. That's the wrong way round. Someone who does something bad may be either sane or insane, you can't determine their mental state by looking at the crime.
Perfectly sane people do bad things all the time, all the way from speeding (which tends to be socially acceptable but can be ruddy dangerous) to mass murder.
And it's very unfair to people with mental illness to lump them in with dangerous criminals. If you look at your odds of being killed by someone else, you are far more likely to be murdered by a sane person than an insane one. (Thankfully in this country you'd be ruddy unlucky to be killed by anyone deliberately.)