That's just the internet, isn't it? You are always going to get insults and back-biting.
I've noticed with other forums that they often shrink, and become reduced to a core set of members, who become familiar to each other, a kind of clique phenomenon. Maybe it's inevitable.
The Ship of Fools has a big membership, about 18, 000, but if you read it regularly, you will also find certain members crop up all the time. I used to read Rational Skepticism, which followed the demise of Dawkins' forum, and it has also shrunk to a clique, (and Dawkins' one had 60, 000 members).
Gonners is right, the Beeb attracted people because of its name.
Let's face it also - religion can become very boring.