I think "called for" is framing it a bit too harshly, although the implication was definitely there. Whether Trump implied that the Second Amendment guys should do something about Clinton or her Supreme Court nominee also isn't clear. Politico gives about as fair of a treatment as one could give to Trump's statements. Here's the actual quote, with some context: “Hillary wants to abolish, essentially abolish, the Second Amendment,” he said as an aside while smiling. “By the way, and if she gets to pick her judges, nothing you can do, folks. Although the Second Amendment people, maybe there is, I don’t know. But I’ll tell you what, that will be a horrible day.”