It's a real shitty thing to get fucked over by an airline when traveling. But in the end it is their aircraft and their business, it's not public transportation. I think they have the right to refuse service or bump people, legally. I know it sucks when it happens because it's often out of your control. But if it happens, act like an adult, not a petulant child. If the airline asks you to leave the aircraft then you must do it. At that point the decision has been made, they aren't taking off with you on it. Refusal will only get you marked as a "troublemaker" and you could end up on a no-fly list. In this day and age there is no fucking around with safety and security on a plane.