You have no contract with Google though. You're literally siphoning on what is a really low-barrier, dare I say free service.

They didn't screw you over. You chose to use them. You didn't pay them, they're paying you.

If you don't like that arrangement, feel free to join a partner agency that can buy and sell ads for you on the ad exchange or go to a different ad network.

Then, if they do something you don't like, you actually have very real power to compel them to do something.

Remember, you get what you pay for.