The line between both is rather blurry. Complaining can range from "this server sucks" to "you're not doing good in this area on the server, here is how to improve it"
The best solution I've found, which actually solves many problems, is to just take every remark someone makes as well as you possibly can.
"You are a stuffty host"
"Sorry, I forgot to take a bath after rolling around in an overturned porta-potty"
"These guns suck."
"Would you prefer changing it to DWeapons, nEkram's, or Advanced Weapons?"
"You never ban people you handicap"
"Ok, let's start with you."
Etc.