I almost got arrested last night for breach of contract? Is this legal?

breach of contract is not a crime. If you want to test a cop and see if an arrest for disrupting an event is a lawful arrest, then leave, get arrested and make the motion to dismiss. Are you asking how a hypothetical court action will play out? No one knows unless they also know what law applies, of what state or nation, and also knows ALL the evidence that will be presented. Every word of testimony. They must also know which bits will be believed and which will not.