No Everton, these things don't "just happen". You and he chose it to happen.
I will say it again. Accusing posters of bullying behaviour is absurd on this thread. If any of Parkranger's defenders care to review threads on Mumsnet where women have discussed their infidelity, you will see that just like in RL, there is a range of reactions.
There are those who say "me too" and display empathy. There are those who say "that's disgusting" (normally because they are raw from the pain of the very behaviour under discussion, or because of their religious or moral views), those who ask difficult and challenging questions - and then there's a curious bunch of posters who are sympathetic, want to know all the details and turn up on every infidelity confession thread to support the OP, while claiming that they aren't unfaithful themselves and are in good relationships .
It's an internet forum that is reflective of society and the diversity of opinion within it. People will not "ignore threads" on an open forum, if they've got strong views, or if they think a poster could be helped by a challenge.
Actually you know, it really doesn't help betrayers to get lots of soothing noises and a whole bunch of platitudes about how "these things happen", "there but for the grace of god" and "it could happen to anyone of us..." as if this were an external event like an earthquake that human beings have no control over and no choice or responsibility for.
It depends what you want from Mumsnet though. If you want support from people and advice about stopping a destructive behaviour, you'll get a lot of help. If you want to carry on with the behaviour, gloat about it, act like a spoilt child and compare an internet forum with a vicious, murderous regime, then you'll get a pretty strong reaction.