"I hate anyone who would use violence against peaceful protesters."
" It's also an essential part of the role of the police officer."
Is that in the job spec? Or just in your imagination?
Your edit misses out a very important point.
The role of the police officer is to enforce the law. (The additional role that's accepted is to enforce obedience to their will, but let's stick to the principle). Laws are invented by politicians and handed down to police. They are instructed to use whatever coercion it takes to enforce the laws.
It is not the officer's role to defy this. If the laws do more harm than good, if they invent or exacerbate trouble, they enforce them nonetheless. Most especially, if the laws change - even to the exact opposite of what they had been - the same police use the same power and coercion to enforce the new law. The example that sparked this thread was deployment to use violence against peaceful protesters. there are many others we could cite, but I'm sure we all get the idea.
The role they take on says 'give me rules to enforce, I don't care what they are as long as they are rules and I get to enforce them'. I cannot see how that is anything other than morally bankrupt; I cannot see how anyone can deny that is the essential role of the police officer.