AT&T is treating all users fairly. If you pay for higher grade service, you get higher grade service. When you pay flat rate, you get full speed to a point, then lower speeds from that point forward. When you pay for metered service, you get your service at full speed for all of it, but you pay more to get that speed. It's much like the "free internet" that T-Mobile offers to tablet users. They get 300MB from "high speed" access free each month, after that, they get throttled down to Edge speeds. If you pay for service from them, you get the full speed for the amount of data you have purchased.
AT&T is being fair to me by not having to charge me more for my service so you have have more full speed service once you have reached your throttling cap. You still have data service, just not at LTE speeds because you are still paying Edge or 3G rates for your unlimited service. Since I pay full price for my LTE data, I get full speed for the amount of data I have subscribed to. If I go over my limit, I have to pay more, but I get it at full speed. If you go over, you don't pay any more, but you get it at a slower rate. I call that fair, in that you can choose which one you want.
AT&T is being fair to me by not having to charge me more for my service so you have have more full speed service once you have reached your throttling cap. You still have data service, just not at LTE speeds because you are still paying Edge or 3G rates for your unlimited service. Since I pay full price for my LTE data, I get full speed for the amount of data I have subscribed to. If I go over my limit, I have to pay more, but I get it at full speed. If you go over, you don't pay any more, but you get it at a slower rate. I call that fair, in that you can choose which one you want.