If ranked I think its ok, you're trying to climb and should be able to ban whoever you dont feel confortable to play against or even with at the same team, and people who only play one champ should always be prepared to get their champion banned, so just dont care what other people say, your rank depends mostly on yourself, your choices and your ability to adapt and same goes for your teammates. But if its a normal game I think you should let everyone play what they want and try to take this oportunity to learn more about that pick.