I, long ago, learnt not to engage with him. He taunts me with silly little insults, which I ignore. I agree with you that if he keeps his nonsense to himself he should be allowed to participate. But the problem always is how he so successfully diverts and bullies. Sending discussions off onto tangents is fair and good - gives the forum colour - but to consistently render every single topic into a slanging match is beyond the pale. There is always someone who seems to give him an opportunity to insult others. I would be happier if you don't give him another opportunity to behave - he has had 18 such opportunities now.