Why would you trust what AT&T is saying publicly? This could have very well been an experiment to "see if anyone noticed", folks noticed, so here's the default "we didn't mean it, you can trust us" explanation.
Major ISPs generally do not act in the best interest of their customers, especially when the action is allowing access to service that hurts their ability to collect more information about their users. They certainly do not deserve the benefit of the doubt.
Not everything is a conspiracy, but nor should plausible explanations be dismissed out of hand without providing evidence or arguments. AT&T has lost the right to be trusted, or even to have the benefit of the doubt, thanks to a long history of anticonsumer activities.
Major ISPs generally do not act in the best interest of their customers, especially when the action is allowing access to service that hurts their ability to collect more information about their users. They certainly do not deserve the benefit of the doubt.