I don't think Knight as the owner of the forum can be held responsible for everything that goes on within it. The very purpose of the forum is to give people an opportunity to speak their own minds openly and freely. It is not a church and he is not the pastor of the church.
I would only say that he and the moderators collectively are indeed responsible to ensure that content on the forum is not defamatory, abusive, racist, sexist, or inciteful of violence, etc. But beyond that each person who contributes is responsible for his own words.
I can appreciate that you are concerned when someone loses his or her faith, as I am sure most of us are, including Knight, but that can't be related specifically to the existence of the forum or his ownership of it. On the contrary, the existence of the forum is a good thing. Or at least, it has been up to now. And it has its ebbs and flows but if anyone no longer thinks it is a good thing then they are free to speak their mind. What will not work is if the purpose of the forum gets linked to pastoral care of its members. If there is to be any pastoral care, it must come from the members themselves, independent of the management.