The mediation committee has refused to mediate in any
circumstance or issue for which I am a participant.
Firstly, it should be noted that this sentence is factually accurate.

But so was the memorable claim by William Clinton:

"I did not have 'sexual relations' with that _woman_... ,Monica Lewinsky!"

The problem with _your_ claim is not the word "is". Rather I would 
emphasize the significate functions of the words "any" and "refuse" 
in your claim.

Specifically, I would point out that you have not raised "any" 
"circumstance" or "issue" on which you would like mediation, and
thus "refusal" is the only option open to any and all mediators
past, present or future. Should you wish to remedy that state, I
am confident that refusal will not subsist.
What is the point of this committee, if it refuses to
even attempt mediation with some of the supposedly
more "mediationally-challenged" users?
Absolutely none. How happy a circumstance then, that this
state of affairs does not obtain!
I think everyone on the mediation committee should be
asked to resign, so that we can get some users who
actually want to mediate and facilitate discussion. 
Here, I would suggest that you start small; try to impeach a
specific mediator. Like me, for instance.
It seems clear to me that these people only took the
position because they saw it as a way of becoming
"super-sysops" -- not because they really wanted to
undertake the effort of mediation. 
Your perspicacity is awe-inspiring. For myself, I never have had
_any_ wish to "undertake the effort of mediation". What I _do_
have, is the wish to do _anything_ that will aid in improving the
way that Wikipedia functions. 

Respectfully (barely),

Jussi-Ville Heiskanen 