His perception is that he was hurt in an unforgivable way by the frum community. He then dedicated his life to revenge this.
The big question is what happened all of a sudden that he stopped.
Based on his own story, which he proudly posted on his website, you can hardly call his hurt "unforgivable".
I believe it has to do more with his own arrogance. He is a strong-minded uber-Liberal like Michael Moore, and believes that Orthodox Judaism is the antithesis to everything that he believes in.
He writes himself that his Judaic beliefs have "evolved". He went from disliking Orthodox Jews to being a flat-out apikoras. Slowly but surely he started to mock Jewish Holidays as "fabricated" etc.. But then he would write that he won't be posting on his blog during those Holidays. Schizophrenic?
What kept him going was his dozen or so minions that would egg him on in the comments every time he wrote one of his warped philosophies. The more hateful and venemous the post, the more of a saint he was for posting it.