They chose a default, the choice to change that default is still with the customer. It's also very granular so you can choose for each individual line how you want your service.
While content manipulation would give pause for concern, as it does with Comcast's data cap notifications, that isn't what T-Mobile is doing. They're not altering the traffic, they're altering the transport rate which is very different. By lowering the bandwidth of certain content types, they're triggering the adaptive technologies employed by services to behave differently.
One of the EFF's gripes was that the pipe constriction was indiscriminate and thus services that didn't employ adaptive technologies experienced buffering and stuttering issues. That's probably the only legitimate point they made.
