If, after everything that's happened, you still think the cops are on your side, you will be the next one who gets punched in the face and run over by a motorcycle. Also, this:
Cops will detain you using whatever amount of physical violence they feel like using. It will almost always be wildly disproportionate to whatever crime they are alleging you have committed. (Remember, you don’t have to commit a crime for police to detain or arrest or hurt you. That is how police work. They will hurt you and detain you first, then allege a bunch of stuff later.) In a protest situation, where there are lots of cops and lots of people to be arrested, this any-means-necessary modus operandi is often intensified, cf. macing wildly into crowds, random batoning, etc.
Also, you don’t have to be “committing” a “crime” to be violently arrested and detained. It does not matter what you’re doing (just ask Oscar Grant). Cops make arrests because it is their job to make arrests: in New York it’s an open secret that quota systems are in place among mid-level police administrators, meaning that more arrests = job security. (Which side are cops on in the class war, btw?) You just have to be in the wrong place at the wrong time. Police are accountable to basically no one, which makes unfounded arrests not only easy but necessary to the job description.
Whether cops are swinging and spraying into crowds or just hanging out on your block, it’s important to remember that your fourth, fifth and sixth* amendment rights are basically nil. You will not be told what you are being detained/arrested for. You should think of these rights with the same beleaguered cynicism with which you regard all liberal notions of subjecthood (or lol if you believe you have rights maybe you should just leave right now—go get arrested and report back, in fact), and the cop who abides by your constitutional rights to, say, know why you’re being detained or to be detained “without” excessive use of force as the exceptional cop, who goes above and beyond for reasons maybe having to do with your (yes your!) perceived socioeconomic status, or maybe just depending on the cop’s mood.
Basically, remember that police are allowed to have guns and whoever has guns can usually do whatever. Excessive use of force is what is regular for people who get arrested, as is the routine denial of constitutional rights to alleged criminals.