Precisely. If you prevent people from saying certain opinions, that will only galvanize them further. And it will make it so that people start to wonder if the person censored has a legitimate point.  It's best to support peoples' speech, no matter how deplorable according to your standards, and defend their right to say it. Stupid ideas will then be rightly pointed out as being stupid and there can be a proper debate. Hopefully the audience to such debates then sees who is genuinely right or wrong based on the weight of evidence and their ability to argue their point.