True. Outright trolling is totally fine to be deported. If they come here to provoke and troll us, fire them to hell and beyond. But in this case the guy, whose message is now deleted, had a fair point in regards to free speech - even if slightly provocative.

For example if messages get downvoted into oblivion - make them hidden but expandable instead of being deleted. If they get downvoted even beyond another threshold, delete them. That would provide some level of user self-moderation, and give censorship a gradient.