I think some easy-handed moderating is a good thing. You don't want to screen out all controversy, but you do want to keep messages out that are intended only to be irritating or instigating.

I co-moderate a group in my profession, and it's not burdensome. The primary screening for that particular group happens when someone wants to join--it's not automatic. The interested person simply has to state briefly the reason for wanting to join the group. You can learn a lot from just a few short phrases!

Lee