Is downtown Seattle a OpenCarry legal zone? If that is the case, and the persons are carrying unloaded firearms openly, and meet any other conditions of such a law, then they are in compliance, obeying the law.
That has been the case at demonstrations where protesters were openly armed, inside the State House as you noted in one case, and those protesters were within the law when they were protesting, or arrests would have resulted, and been expected to happen, to uphold the local LAW.
I was, and am, unaware that the occupiers of some seized city blocks of homes and businesses and streets are within local law at all, and that the local law there includes open carry of firearms. Does the local law state such openly carried firearms be unloaded? Do citizens who carry need some special training in Washington State, and do they carry some documentation to certify the local law in that regard?
Just wondered, and if they are fully legal, then I withdraw any complaint.