PPRuNe is not a democracy, and nor is it a members club (well as far as I am aware). It is a forum to discuss matters of mutual interest provided by another party.
Having contributed for too many years, in my experience it does a pretty good job. Most private pilots either come here or to Flyer.
Inevitably when contributors get banned, stir the pot, or are generally obnoxious it causes lively debate - and lets face it perhaps there is a little bit of old women in us all.
However since its not our forum, those that own it have the right to operate the forum as they see fit. It seems to me if we don't like it then everyone has the right to go elsewhere.
Personally I think over the years they have done a pretty good job. They have often allowed debate that I would have thought crosses more than a few lines of "reasonableness" - and good for them!
I dont think the owners have any obligation to explain why they have removed threads or contributors, and more to the point, there could be a host of reasons for doing so that you certainly could not make public.
As with any organisation the owners should of course abide by their own rules as much as the contributors.
Those that would like to see things run differently, good for you, I am not criticising you and all credit to the owners for allowing the debate. As with any organisation you can have a go at changing the way in which it operates but dont get upset if the owners thank you for your views but do nothing.