> It's suspicious but legal, in the same category as carting a semi-automatic into a grocery store in an open-carry state.

Any suspicion toward a US citizen for open-carrying a semi-automatic weapon (which you realize is like half of the handguns in circulation, right?) is entirely due to one's own prejudice and misconceptions. It is objectively not suspicious. The individual is openly carrying it, not hiding it. Concealed carry should not be suspicious either, but open carry should be less suspicious.

This would be a good moment to examine your biases against a fundamentally protected human right as recognized by our constitution.