This thing is, they might not have a warrant but they can come into your house if they want. They can toss the place, etc. Your rights don't come into play until you go to court, where it will cost you a lot of money to excercise your rights. Disobeying a police order to disperse is the same way, you don't get to decide if the order is lawful, the police can arrest you at any time and haul you off to jail, you don't get a say until you are in front of a judge. Arguably, police need to have that power, otherwise it would quickly become impossible to do the job.
Aside from an arrest being quite punative in of itself, the biggest flaw I see is that there are really no consequences for law enforcement who heap bogus charges on people. Hence some places (florida?) where the police are increasingly arresting people for resisting arrest just for asking why they have been arrested etc.