First, Carl does a damn good job with his web site, and I for one am very grateful to him for the service he provides. As the owner and controller of the web-site he must control it as he sees fit, and if any user dislikes his control they should stop using the site; it would be reasonable to tell Carl why though. I do not know anything about the offending post, but Carl's defence here seems reasonable.
Secondly, there is no reason why the internet should be free of controls, and that means that web-site owners must police, or censor, information that would be harmful to others or themselves. Getting involved in conflicts that may involve litigation is a sure way for a web-site owner to create trouble for himself. The only really difficult problem that the internet, and particularly a forum on it, creates is that the content is added and seen in differing countries, which have different laws and customs. However, there is no reason why the criminal and civil laws of all countries cannot be applied to the content found on the internet, and there are many reasons why such laws should be applied; unfettered free speech is a very bad thing. As far as I can see, Carl is being eminently sensible in trying to avoid vitriolic attacks on people and companies that appear on his site; criticism can be a very tricky thing to get right. I have no criticism to make of Carl in this regard, even if he has smacked the back of my legs when I have been a naughty boy.
As a postscript, I would also add that there has been much criticism of Carl for dropping his reviews of Sony Alpha equipment for the forseeable future, and I feel that much of that too has been quite unfair. Anyone can think of a dozen good reasons why he might have to do that in about as many seconds, and I respect his motives for not making his reasons public. Nobody is perfect, and I am sure Carl isn't any more than I am, but all I, and most of us, know of him is through his web-site, and on that he has done a very, very good job.