Hopefully this will clarify things.
If the police have you, and you know they have you, own up to your actions. If they claim they have you, but don't, then by all means assume the role of adversary.
But the police do not have the final say so. This is ultimately up to a judge. But you, as a person, who did or did not commit a crime, know if the police really have anything on you or not. This is where knowing your rights is paramount. No, telling the cops how wrong they are probably will not get you anywhere on the streets, and a judge may not like seeing someone who is anti-or-combative towards authority, but if they really have nothing and they are arresting you anyways they deserve to be called a ****ing pig, you should not give in and go easily, and you should definitely not hit them (unless they are about to sexually assault you, then by all means beat the living **** out of them if you think you can because road side cavity searches are very illegal, and it would bring the national attention that is deserved of pigs raping people). This does require a strong degree of self-honesty, and it is absolutely necessary you know your rights and know for sure, beyond any shadow of a doubt, that you are in the right and the cop is in the wrong, but it is very much better to have fought and lost than to not have fought at all if you are being wronged. Unfortunately society has reached a point in which it will take a number of innocents being martyrs to even begin to correct the grave wrongs we, as civilians, have been subjected to at the hands of those who have sworn to protect and uphold the law.