While I agree with your last paragraph, the bolded sentence bares comment: the only person that was 100% perfect was crucified BECAUSE He was 100% perfect. That makes all of us less than 100% perfect as that psychologist said.A psychologist once remarked that we all have at least some form of mental illness... nobody is 100% perfect. Most of the time it doesn't affect our daily function, but merely helps shape our personalities. That being said, it's hard to draw the line as to what makes someone sufficiently mentally ill that they would be considered a danger to themselves or others if they owned or had access to dangerous objects or weapons. It's just as easy to point the finger at mental illness as a cause of mass shootings as it is the legality of firearms... and both would be missing the mark. Plenty of people with mental illnesses own firearms and never hurt a soul. Plenty of others have never been considered mentally ill in their lives, and yet one day they suddenly act out on a silent urge to kill people.
The problem is far too complex to simply say we need more laws against guns or mentally ill people... unless the plan is to either ban ALL guns outright or lock up everybody who acts strange against their will. It seems the Democrats want to do the former and Republicans want to do the latter.