The 2nd Amendment is a Positive Right. Like the 1st. Which is to say that it's not incumbent upon the citizen to "prove" that they should have it, but rather incumbent upon the State to prove that they should not. Would you vote for a law which suggested that someone should have their 1st Amendment rights abrogated because the Government believed that, based on their prior behavior, they might "scream 'Fire!' in a crowded theatre"? I mean, even provided that such a law were Constitutional, which it seems to me that it would obviously not be. The thing about rights is that once they're gone, they're almost impossible to get back, whereas the opposite is almost never true. Treating them casually (or hysterically) is a receipe for tyranny.