1 Should the punishment fit the crime and does it currently?
I can't see anything here I'd call "a punishment".

2 Are all the volunteers authorised to administer summary justice and censor other's postings – without the poster's knowledge or permission – based only on their value judgement?
That seems a reasonable way of doing it to me - if someone with this role makes too many mistakes or is acting maliciously, they should cease to be allowed to carry on. "Summary justice" is a hyped up expression in this context. This isn't a spaghetti western.

3 Is there to be no difference to be seen between an abusive post and say an incoherent one?
Where people abusive posts it is appropriate to try to discourage them from doing so; people who make incoherent posts may benefit from being helped to avoid doing so on occasion. In both cases it might sometimes be appropriate for the posts to be removed,

4 Is a sensible and responsible example being set when our volunteer police force also indulge in making abusive posts themselves and start calling other posters names?
Courtesy is always appropriate. So is plain speaking. (And if you think that those PMs from Joe are "abusive"...)

5 Is it really too much to ask that those that would volunteer to judge (and punish) us – can be expected to always set the standards and be judged themselves by these standards?
Not too much to ask, and my experience is that that is precisely what we get.

Basically there are two ways of running things in any community - family, village, nation – one is having a system of laws and tribunals and all that; and is the other involves trusting people to do the right thing. The latter way can break down, and isn't always possible, but where it's possible to do it the second way, and have things work reasonably satisfactorily, that's the system I prefer. That's a personal preference, and I think that in the Mudcat it works pretty well. It's organisationally untidy, but I can stand a fair amount of that.