He hasn't been purged. ie there have been no briefings about him liking tweets he shouldn't have, or posing with unacceptable political figures etc..
It seems that they have been pushed into this because a "serious" complaint was made against him, which no one will know what it actually is until it has been investigated.
It could be something in his private life, something about money, his behaviour to party colleagues or ..... ???
He is saying it is malicious, and obviously submitting a complaint at this point is one way of making sure he cant be selected. So rather than malicious it could be a case of you reap what you sow.
Of course, given the implications of an in group running riot, maybe one of them submitted a complaint as a clever dodge to avoid saying he has been purged.
But of course I couldn't possible comment. And nor can the media or anyone involved in investigating it.
Revenge is a dish best eaten cold.