Well, for one white supremacist terrorism is responsible for the vast majority of terror attacks in the US lately. And Trump and the Republicans hold the levers of power that could actually do something to enact gun control.
Like I said earlier, there's nothing to point to a political (or any at this point) motive for the Dayton shooting, although hatred of women may have played a part in it.
Yeah, he was a leftist, the right doesn't have a monopoly on deranged lunatics, but we aren't experiencing a spate of out of control leftist terror attacks.