Charging a person for protest is a complete violation to a person. You have the right to fight against anything that you don't agree with. The moment you cant you are a soul less slave. Better to live free amongst the chaos than as a slave in a false security bubble.
Let me start by saying that I meant to type Human rights violation (YES) or necessary evil (NO). I can't go back and change that, sorry. :(
With that aside, I believe unlawful assembly charges are necessary. Although freedom of assembly should be protected, it should not infringe on others' rights to a peaceful and tranquil community. In the case of unauthorised protests, or authorised protests turned ugly (but not yet turned into riots), it is necessary to have a law with which the police can charge the protestors. There may be political prosecutions, but that problem can be avoided with an independent judiciary.