Your best bet is to stop reading what his posts. If you read what he says, you'll feel a compulsion to answer. He thrives on that.
And I wouldn't worry too much about others being "misled". Some folks need to be misled a few times in order to learn the ability called "discernment", and moreless could be providing a valuable service for such people. (I know a little bit about this myself....) Others will read what he says and take from it what they find useful and dump what they don't. And still others will rise to correct him and continue the fight.
The drama continues... always changing, yet always the same...