Forum health is not about free speech.
And the people who are most upset are this are those who genuinely believe in free speech. I did too.
It's only after seeing many forums devolve that its clear to me and many other mods, admins, writers and foru users that forum operation, forum discussion health and real world free speech do not overlap perfectly.
Free speech is great so long as it doesn't descend into anarchy. And when that happens, you're effectively in a situation where nobody really gets chance to say anything because the forum is flooded with hate. So it sometimes takes a little weed killing to allow comments to fully blossom.
We should also bare in mind that there's a difference between hateful comments and trolling - which are only posted to offend, and unpopular or incorrect statements. Sometimes unpopular comments will lead to heated discussions; it's a pity when that happens, but that's sometimes unavoidable because humans are often passionate beings. But generally such comments shouldn't be down-voted (instead the helpful, insightful or correct arguments should be up-voted). The only comments that should be down-voted are the hateful and trolling remarks. And when it becomes clear that such remarks are inducing anarchy, then it's clear that stricter moderation is required to restore the balance so that everyone else doesn't have their freedom of speech removed due to the lack of an open discussion on the forum.