Well, what they actually seem to be saying is that network neutrality should protect against discrimination based on user, application, content or other details

Well, what they actually seem to be saying is that network neutrality should protect against discrimination based on user, application, content or other details that are irrelevant to network transit. The argument is that performance requirements are something a bit different and there is a need for market to allow for competition on performance without allowing discrimination based on the other aspects of the traffic. The idea being that if your ISP owns a game company that makes a popular FPS, they shouldn't be able to charge higher rates for packets that need high performance based on the fact that those packets are carrying content for a competing FPS.