If Netflix really wanted to turn this around on AT&T, they would just have different prices based on how much each provider extorted from them. Comcast customers would pay more for Netflix than Cablevision customers. Netflix would pay the tax, then pass the cost onto the customer, but not onto each customer equally. It would then publish this data for all to see.
I've been told that credit card companies simply forbid this sort of thing as part of their contractual agreements with merchants. Comcast appears to have similar leverage, so I imagine they would do likewise.