Edit: It's the same way that when you agree to the TOS of a service like, xbox live or something, if they had a line about how you can't talk badly about Xbox or they delete your account, it's not breaking the first amendment, because they aren't the government, and you consented to that agreement.
Services are different from rights.
(The fact that AT&T's ad-supported plan is not a better deal than Google's fiber plan is not really material. It isn't generally illegal to have an inferior product or to charge more than your competitors for the same goods.)
NOTE: A "normal" complaint is different from outright excessive/exaggerated slander.
You're not paying $30 extra to opt-out. They're giving you a $30 discount for you to hand over your data.
It's the same way gas stations get away with "charging extra" for credit. Most credit card vendor agreements do not allow the merchant to pass along the 3% or whatever fee to the customer. So what the gas stations do instead is give you a "cash discount".
That's why you have to read contracts very carefully.