A dozen people showed up to protest Obama's VFW speech openly & legally carrying weapons. I'm a strong supporter of the 2nd Amendment, and it's good that Arizona has more freedom than some other areas of the country. But at the same time, I'm not sure what these people hope to accomplish.
Armed individuals at a presidential event create an additional security concern for the Secret Service and increase the chances of an unfortunate incident. What if someone makes a move that could be interpreted as a threat? The Secret Service has to err on the side of protecting the president. That could lead to someone getting killed by mistake. In addition, regardless of their actual intent, carrying weapons to a political protest will be interpreted by some as an implied threat, and an attempt to intimidate. It also feeds into left-wing hysteria about the menace of right-wing extremism. All in all, I don't see the upside of armed protesting.