The original open letter Moore wrote to encourage Clark to run indicated this whole relationship was based on one incident.
Moore, getting bashed by a Fox interviewer the day after getting boo'ed at the Academy Awards, was summarily dismissed as "crazy" but defended by
(of all people) a 4 Star General, also on the program.
Note that Clark didn't defend what Moore said about the war, just acknowledged that wars are fought so people like Moore can say them.
And I believe Moore's problem with Dean is gun control (or lack thereof), whereas Clark has said: If you're the type that likes semi-automatic
weapons, we have a place for you in the US Army.
Of all the big shot 'liberal' endorsements for Dean, somehow this one rings truer for me. From the heart, no hidden agenda.