(A)llusions to “gun violence” and “mental health” are especially pernicious inasmuch as they obscure the evil nature of the deed being explained. To see just how egregious an offense this is, consider some analogies. Imagine if, while discussing the Holocaust, we spoke about “gas chamber violence,” or while discussing Islamic State mass beheadings, we talked instead of “machete violence.” Or suppose that discussions of the lynching of blacks were peppered with references to “rope violence.” None of this would sit well with decent human beings, for it is clear, or at least it is thought that it should be clear, that such descriptions miss entirely that which is fundamental to the phenomena being described—the perpetrators responsible for these wicked deeds.
Of course the reason the collectivists blame "gun violence" and seek to expand the definition of "mentally ill" as pertains to restricting the availability of firearms is the traditional method of such people to win the argument -- citizen disarmament -- by framing the question and corrupting the language. Buy into that, and they've won the argument already -- an old Communist trick. Remember, they think anybody who resists them is, ipso facto, mentally ill. Why do you think they call us "gun nuts"?
Besides, admitting that there is unrelenting evil in the world leads back to the Devil which leads back to God, and overarching moral authority other than their own cannot be conceded or tolerated. It was not accidentally that Obama criticized people who "cling to their Bibles and their guns." Collectivists view both as deadly dangers to their appetites.