If you adamantly refuse to even hear an opinion or point of view that differs from the one you've been taught to believe, you don't actually believe the one you've been taught. A genuine conviction doesn't waver from something as flimsy as mere exposure to disagreeing ideas. If you fear that hearing an idea that deviates from the "right" ones might make you accidentally adapt it, get the two confused and forget which one was the "right" and which one was the "wrong" idea, and get rejected by your peers by accidentally echoing the wrong kind of thoughts, you don't actually truly think that the things you've been taught as right are right.
Not because you would somehow deep down secretly think that the "wrong" ideas are "right" and the "right" ideas are "wrong", but because you simply do not actually think at all.
