I am glad you brought this up. To me it goes to the heart of the issue, and the point to the thread.
The last several years have seen an uptick in the sort of senseless, ideological, violence and shooting we are talking about here. From the #BLM snipers shooting Dallas cops to the Orlando nightclub, from Bible study groups to women's clinics, and now this. Shooting up some guys practicing ball.
The perps have almost nothing in common, ideologically. They have wildly different religions and ethnicity and political leanings. But they obviously do have one big, defining, thing in common.
They all were convinced that violence, specifically gun violence, was the way to solve some social issue they felt otherwise unable to address. Not peaceful protests or democracy or anything like that. Guns.
"Guns are the solution" is not a liberal message. Not all conservatives promulgate that, but almost everyone who does qualifies as a conservative in my book. From the NRA to the talk radio hosts to Trump, the premise that guns and violence are the solution is a conservative trope, not a liberal message.
So yeah, when the NRA sends messages like "An armed society is a polite society" and "Go get more guns and ammo before the government takes away your 2nd amendment rights" and stuff like that they are one of the biggest, if not the very top, corporate instigator of violence and homegrown terrorism in the USA. Those messages don't only go out to mentally stable, trained, responsible citizens. They also go out to the nut cases and people off their meds.
So yeah, I blame the NRA for a lot of the violence, including the shooting of the Republican congressmen on the ball field. Not "liberals".
Tom