Aaah so the crew are the verbal punchbags for the passengers and should take everything with a smile? How about a little respect from the passengers for the crew? I very much doubt this was a 'replacement' crew, more likely they were the crew originally scheduled to operate on the day and were in no way at fault for the delay. They may not even have known about it until they got to the aircraft. If some smart ass passenger wants to get all sarcastic before he even gets on board then off-loading him will teach him a lesson in respect. The crew aren't there as his skivvies.
As for the airline overstepping their authority, pu-lease! You buy a ticket it says A to B on it, and the airline are under no obligation to get you there at any given time. They can refuse to carry you at any time, and if they suspect you will be disruptive on the flight then they can off load you. Thats their right. If the guy didn't want to be off loaded then he shouldn't have given the Captain sh1t. You think the TSA would take a more forgiving line if he got call @rsey with them?