Free speech builds up our immunity to dangerous ideas. But we're starting to act like overzealous parents who think the best way to keep their children safe is to make sure they never come in contact with any germs.
A lack of exposure to bad things doesn't make a person or a society healthy, it just makes them fragile and intolerant.
If we run around in a panic installing ideological hand sanitizers everywhere, our intellectual defence systems are going to break down. The truth is they already have: We're becoming hypersensitive and intolerant. We're starting to treat every little annoyance as if it was a mortal threat. And, now that our fears are being continuously amplified by the positive feedback loops baked into social media, we're starting to believe that our entire culture needs to be ideologically sterilized to protect us from bad things. But that's futile—and dangerous. There's no such thing as a truly sterile environment, not even in a hospital. And we need to be exposed to a complex ecosystem of ideas, some good, some bad, so that we don't become weak and fragile and susceptible to truly awful plagues like authoritarianism.
Now, you could argue that some institutions in our culture need to be sterilized as much as possible. Our courtrooms, for example, should probably be treated like operating rooms: there are lives at stake, open wounds exposed, and judges and lawyers should have a damn good scrubbing on their way in. But we can't treat all of our society like an operating room. It's ok for our culture to occasionally get sick and have to sneeze and cough to get rid of something nasty.