I think there’s a difference between challenging and shutting down. Challenging should be encouraged since it (at least theoretically) forces people to have a reasonable basis for their beliefs. Students who don’t want to be challenged and just want to be correct and shut down opposing thoughts shouldn’t really be called students. They’re not seeing to broaden their horizons. If they only want to learn about their speciality topic, that’s okay, but university isn’t really the place for that. Technical and speciality schools exist to focus on small fields of learning.