Good mods can tell the difference between people who have other views and idiots. If the moderators in your community of choice can't, you should probably choose another community. But your equivocation between silencing other viewpoints and eliminating unhealthy voices is not useful.
For example, in this community, anti-startup articles get posted occasionally. I'd expect to see far more dead comments from people who post agreement with such articles. But I browse with showdead on, and I see no such thing.
Basically, the rhetoric needs to line up with the evidence at hand. If it doesn't, it's unsound.
There are many examples in real life when authorities use pejorative terms such as terrorists, criminals for people who show disagreement.
The moderators of the particular community, who else?
For example, when 4chan became Anonymous, a lot of people objected to the politicization of the community. They felt that it was a betrayal of the original purpose of the community. But communities evolve. Purposes change. We don't live in the Founding Fathers' America anymore. It's not easy to ban people who "disregard the purpose of the community" without also trampling on nascent attempts to evolve that very purpose, and I suspect that this is where accusations of censorship most often arise. Strong moderation, on its own, can't solve this problem.
Good moderators should be wise enough to make subtle distinctions like this and humble enough to confer with long-time users on tricky issues.
The fact is that at every point in the development of our culture, most people have been horribly misinformed about many important things, and when someone came on the scene and questioned one of these things, he was thought a fool by the majority or even imprisoned (Galileo) or burned at the stake. There is no reason to think this groupthink isn't integral to our present culture, including by scientists and professionals; quite the contrary.