Both of the people were mentally ill. Bibeau, the homeless Ottawa killer, had a history of violence, drug addiction, and mental instability, including 12 convictions in Quebec between 2001 and 2011 for crimes including drug possession, impaired driving, weapons offences, assault causing bodily harm, theft, and possession of break-in tools, which started long before he converted to islam.
Mentally ill by what standards? You (or others) didn't like the way he acted? I can find no evidence of any clinical diagnosis of any mental illness for Bibeau-Zehaf, though he was a convert (though his father was Muslim and Libyan). Your claim is that despite his Islamic family heritage, despite the fact that he had converted to Islam for "all the wrong reasons" over decade ago, and despite the fact that he had family members fighting for jihad abroad, he was was just misguided due to some previously non-diagnosed mental illness or possible drug use? That does not seem logical to me.
Rouleau, the Quebec killer, had been taken to a psychiatric hospital by his father, but they couldn't keep him when he said he wanted to leave. He had drug problems, had to be in a special school for kids with discipline problems when he was younger, his personal life had fallen apart, his business had failed and last year at 24 he turned to islam, looking for something to cling to where he wouldn't feel like an inadequate failure, and was attracted to the extremists on the net and in the media.
Your argument for Rouleau is perhaps more apt, since you avoid the unverifiable claims of mental illness, but you make a huge error. You assume that converting to a new faith due to some kind of adversity is "all the wrong reasons" and implies (or infers) metal illness! I think you are perhaps not very clear on how religions tend to start and spread. Founders, missionaries, and other zealots always target the margins of society. Look at who Jesus hung out with--the disaffected. Look at who Muhammad hung out with--those whose power was distinct from the dominant tribal structures (and look at how he targeted the weaker Jewish clans after several military setbacks). Look at Buddha and his life as an ascetic. Look St Francis. Look at how both Christianity and Islam spread in South Asia--starting from the dalits--the disaffected. Almost universally, the most powerful religious symbols, figures, and acts, involve those who are somehow disaffected. To trivialize this is a huge mistake.
That brings us to today. Despite what you might want to believe, Muslim belief in what we in the West would call "militant Islamism" is pretty darn popular and pretty widespread. There are many opinion polls covering Islamicate countries across the world that back this up. There is a strong militant missionary movement. Giving the religion/ideology a pass and writing off incident after incident as "merely" a lone wolf makes absolutely no sense.
Most people are able to make the distinction between a nutbar using a religion as a smokescreen to their using violence to escape their own failures or shortcomings, and the majority who peacefully practice that same religion. This applies equally to muslims, christians, atheists, or whatever your personal preference or poison.
I disagree with this incredibly strongly. Religion, ideology, and violence are so tightly intertwined they almost cannot be decoupled. Today, Islam clearly holds a siren's song appeal to some disaffected members of society. You give the religion/ideology a complete pass. Have you not considered that the religion/ideology places a major role in motivating these individuals to commit their heinous actions?