And, like it or not your way of parenting is just that 'your' way, and it doesn't mean it's the 'only', 'correct' or the 'right' way!! And comparing the adult 'international' members here to your children is pointless and belittling to the case at hand.
The main issue here is that the op was 'suddenly' requested to change his long term avatar on the spur of the moment, due to 'one' persons complaint, and a mod agreeing with them of the interpretation of what is a professional avatar. (One persons pov a new rule does not make!) If avatars and their interpretation-of is a 'now' issue/problem with NP policies, then it should have been noted for all members prior that offensive avatars will need to be removed along with guidelines as to what is 'offensive'. But the now enforced never before known rule and action of "I'm the mod and you do as I instructed or I'll do it for you", was over handled, and came off as mean and authoritative, hence why the op reacted as he did.
Mods need to make 'new' changes/rules noted for all to know of and when so before enforcing, so everyone in on the same page. And the power hunger needs to be curtailed and used when necessary, not ad hock.