How do you draw the line between mental health and evil, is there even a line? Does it matter? I would say the results of their acts matter the most. Don't you have to be a little crazy to kill someone for any reason, but if there is a group of people out there taking advantage of disturbed individuals, pushing them into and directing to some degree their acts, even if it is through hateful rhetoric more than direct planning, isn't that still something that needs to be addressed?
Is everyone fighting in the middle east because they are mentally ill or because they believe they have good reason, because they have the right ancestry or the right rules with which to live by, at the end of the day they are still killing people for their beliefs, just like this guy in Ottawa did. Crazy or not, it's not something you shrug your shoulders at and say, o well. There is no question they did this in the name of their religion, without that push they might have been like many other Canadians who suffer with mental illness who could use more help, that doesn't mean you ignore this reality. We have enough sick people who commit violent acts without extremists creating more of them.