Ultimately he is the group leader and can decide who he wants to take. If I were you i'd just move on.
I know when I was going through my "run nothing but pugs" phase I ran into A LOT of bad players of every form and build. Maybe he just encountered one too many "battle clerics" who refused to heal or only would on themselves and decided a blanket ban was the solution.
Its awesome you found a good cleric, they are rare if the compliments and requests for friends I get when I do runs is any indication. Funny enough I think of myself as only above average because when I play a healer I don't melee, I keep my party alive and cast CC when appropriate.
I have seem some amazing healers who could do what I do AND contribute more.
D.W.A.T - Thelanis
Dilim - 13 Archmage TR1 ~ Pugna - 10 Pale Master ~ Vorstellung - 20 Cleric
Kobold - The other white meat.
I disagree.
The groupleader behaved badly. He cost the party a good healer and delayed the start of the adventure accordingly.
But someone else behaving cluelessly does not give you the right to be even worse. Waiting in group then hosing them with multiple reentries makes you a worse jerk than the stupid leader. He acted from ignorance. You acted with full awareness of what a jerk you were being.
Not only that, but you make it less likely that the leader will learn from his mistakes, since you change his outlook from "I wonder why that guy left right after I dropped his friend" to "Gosh, that guy was a childish twit. I'm glad I dumped his idiot battlecleric friend who was probably even worse."
If you want to help the game, control your own behavior. You cannot control anyone else's.
Give a man a fish, and he demands two more tomorrow.
Teach a man to fish, and he'll leave to find somebody who'll just give him a fish.
Beat him unconscious with the fish, and it's comedy.
I suppose it's pointless to clarify as people have already gone on a gleeful neg-rep fest due to the other post, but at the time this cleric was invited, the leader and I were the only two in the party and he was trying to rebuild it. Not your fault, I typed "A 6th" in the first post instead of "A 6th level sorc".