There are different ways to leave, some are productive and some are not. Have a discussion that is productive and understanding why someone left is different than listening to people bash on the church, members and constantly make bad remarks.
It is like breaking up with a GF. If the GF has a good discussion, you understand each others points and move on. There are ex-GF's that spread gossip, do anything to attack you, make up things, cannot focus on one positive. Huge difference. One is productive and one is not.