Because they were by their right truly peacefully protesting and not looking for trouble.
You seem level headed compared to a couple others. Why the trouble distinguishing between peacefully protesting and antagonizing/interfering/blocking/spitting at or throwing rocks or dildos at agents? They aren’t the same thing as you guys attest them to be.
I look at thru the lens of "would I be justified in (doing whatever the cop did) in that situation."
if the answer is no, the cop is hiding behind his badge, and probably not acting in a healthy to society way.
someone gets in my way, even if I am on the job, I don't get to shoot them. someone interferes with my job, I don't get to shoot them. For cops its a bit different, especially if they are dealing with a life/death situation that is being interfered with, that gets "ok'd" by me.
similar situation when its not a shooting. if the cop goes thru at least two levels of alternate means of dealing with a situation before shooting, its also "ok" with me. I don't expect them to put up with actual physical harassment indefinitely. someone getting in their face to curse them? no way, cop needs to stay in line.
so the old man getting shoved, doesn't bother me. the guy pinned to the ground getting arrested and shot in the back when the cops found a gun on him? Completely unjustified. that matter had been resolved. I don't get to shoot a home invader who is face down on the ground, even if I notice he has a gun on his person.
and I am definitely making a distinction between what I "should" do, and what I might be able to get away with a court. just because the system protects the cops doesn't mean a particular shooting/interaction was an acceptable one.