Ignoring the issue of whether one can clearly distinguish between--or accomplish--network management and network neutrality, one frustration some of us might have about network neutrality is the insistence that packet prioritization is simply wrong, always and everywhere.
That arguably is not the case. Under conditions of congestion (when network management is required), user experience benefits from packet prioritization (non-neutral treatment) to preserve experience of apps that are highly sensitive to latency, such as voice or videoconferencing, for example.
Now T-Mobile US says it will--under conditions of congestion--prioritize traffic used directly by devices connected to the mobile network, compared to traffic used by tethered devices.
In other words, the management choice is to preserve smartphone experience over that of tethered devices, when the network is congested.
That is a preference for supporting user smartphone access (implying more preference for bandwidth supplied to customers when out and about), compared to customer use of their devices for tethering, presumably implying stationary usage settings.
To the extent that all networks are built with contention in mind, there always is a need for network management when congestion occurs. No network is built on the assumption that all conceivable customer demand, at the peak hour of the peak day, always will be supported without congestion.
That necessarily means some amount of network management is necessary. But it is hard to clearly distinguish between management to preserve user experience, under conditions of congestion, and "treating every packet equally."