I have no plans to attend any protests, but I agree with the sentiment that citizens ought to be able to attend protests against the government if they so wish. Seems fundamental to a free society to me.
They also have the obligation to behave peacefully. Those few that do not should be treated as the criminals they are. That's just common sense to me. I expect the authorities to maintain the distinction and I believe, by and large, that they try their best to do so.
(Where's Martin Luther King when we need him? Peaceful protest, especially if the authorities do abuse the protestors, is so much more effective in enlisting sympathy to one's cause than is vandalism and attacking law enforcement.)
While I typically carry a concealed weapon when out and about, I think that if I did elect to attend a protest, I would deliberately disarm before attending. Just too many things could go wrong when armed and in the midst of a mass protest.