First off, I think that it is moderating, not moderatoring.
In addition, I also think that you are asking an unreasonable amount of effort to be committed by these volunteers, because that is what the ninjas are. With an extremely high user to staff ratio, keeping everyone's avatar PG 13 would be a large job even if the entire team of ninjas was active, which they are not. I also do not think that anyone would find it appealing to go through all the images that the users of this site deem appropriate for use an avatar, given the variety of "unusual" users on this site.
Expecting them to do this means you have not looked at it from their point of view. Yes, custom avatars would be nice in many ways, but they are unnecessary with the amount of customization already available that distinguishes user.