Maybe they do and maybe they don't, but that particular argument doesn't work at all. There's a huge difference between a protest (even with armed protesters) in broad daylight surrounded by cops and news media, and a split-second confrontation between a police officer and a suspect in the middle of the night. You cannot boil down both situations to "a person may have a gun."
(To be clear, that's not to make any moral judgements about the people involved in those two different situations, or what cops should or should not do. Just saying they are different, and it's dangerously simplistic to line them up next to each other and believe you've proved anything.)