There’s a difference between a credible threat and an infirm old man expressing a wish that we might not agree with. IMO, the fact that he SAID such a thing proves he’s probably not competent.
I sat next to seniors from 2003 - 2008 and listened them them telling me angrily how “Bush should be SHOT”. Nobody came and arrested them. They weren’t threats, they were opinions and wishful thinking.
There is a big difference between saying "Bush/Obama should be shot" and "I'm going to go kill Bush/Obama"