Or is the worry that only indefinitely free offerings can set the stage for trouble later? To me both viewpoints set the stage for trouble, except the indefinite free offering is a darker shade of gray.
For example, if T-Mobile started charging $10/month to access Spotify on their network, that's an obvious net neutrality problem. What I'm saying is that if T-Mobile lets you access Spotify for free on their network, that is also a net neutrality problem, although many people see it as just a bonus.
Stuff where an entire plan is free is fine. It's when different traffic is treated differently that net neutrality comes in.
A counter example that I bet T-Mobile is waiting to deploy is parental control. As strange as it sounds, there are actually families that pay to have their wireless carrier restrict adult content while on-net.
EDIT: "As strange as it sounds" refers to the fact that most parental control solutions are network-based, when in fact a proper parental control solution should be client-based because as soon as your child goes to WiFi at MacDonalds/Starbucks they probably have access to all the adult content they want to see by bypassing the wireless carrier parental control network controls.
a) eat up more data as the client's parental control component needs to continually update its URL database;
b) require more CPU and RAM (i.e. more expensive phone) if you want a better "content inspection" engine (since URLs are notoriously easy to bypass);
c) you are willfully acting as a MITM and creating a backdoor by forcing all content to be decrypted in some way for the solution to work effectively and only controlled by you (the parent), which may (or may not) compromise your stance on the issue of e2e encryption, privacy and security;
d) (your point above and following from c) having to personally safeguard and secure your child's device;
e) on Android, is it even possible to not root the device? Where's there's a will, there's a way: most kids with smartphones coupled with an incentive to bypass controls (Minecraft was a good example given above) could easily root their device, or eventually social engineer their parents into choosing future devices that are rootable.
My parents stopped filtering my internet at about 8 - I'd been online since 4- and while I'm certainly more scarred and savvy about a variety of strange subcultures than I would otherwise be, I am glad of it. Even before then, the filters had not been 100%; I know by anecdote that I had seen some seriously deranged pornography before the filters completely dropped, and I really just wasn't interested.
And to anyone that doesn't think kids know how to change the wifi settings:
My son is 6. He trawls for open wifi like crazy if I don't start my hotspot. And other kids do to, at an alarming rate: We were flying to see his grandma before christmas and at the gate at London Gatwick, I turned on my hotspot. He was one the iPad that automatically connected. Only I had turned the password off at some point for some reason. Within a couple of minutes, half a dozen kids had joined his Minecraft world by finding my hotspot, and then starting Minecraft and realising there was an accessible local server ....
(alarming, because they'd be an oh-so-tempting target for all kinds of stuff...)
Incidentally, when I went looking for the setting today (it's in your account profile under Phone Controls), I discovered I now have a Binge On setting, which is (of course) on by default. However, I haven't checked to see if streaming video works (even though I have no data plan).
1) they are allowing customers to opt-out (maybe they will concede this could be improved, but it doesn't change their fundamental desire to circumvent net neutrality); 2) content discrimination has positive benefits for consumers (i.e. allows higher consumption of content)
T-Mobile may be willing to bet that the FCC and consumer groups will be hard-pressed to claim that sending HDTV vs. EDTV falls under a discriminatory context given the consumer benefits and (seeming) fulfillment of video service.