Actually that's the point of opinion, you get to decide what you think of other people's causes.
Nobody said you cant protest to your heart's content, you can protest over anything. It's just calling out one of those protests is a mite's buzz of a complaint to a lion's roar of shame for the treatment of black people by America.
You can't decide what other people think is unjust. You would be negating the entire point of protests.
I think the quarantine of the healthy was unjust. You're going to tell me I can't protest against it?