"Sure, those vendors have a "choice". Try to stay in business while being abused by the big boy or go out of business. Yeah, that's some choice. The same sort of choice Eastern European women are given when they are forced into prostitution."
Comparing Walmart to East European prostitution rings? Once again, 'fiddlesticks'.
"Concentration of power is bad. Lack of choices and competition is bad. There is no difference between having to pay a Microsoft a fee when you buy a computer and having to pay a sales tax if your only other choice is, "Don't buy a computer." There is no difference between Wal-Mart forcing prices on a vendor and government price controls if the only other choice is, "Then don't sell those goods." Those are non-choices. Neither Microsoft nor Wal-Mart is quite at that point in many areas but they're getting close."
If you can't see the difference between walmart negotiating prices and government price controls then you need a basic class in economics.
A one sided demand is not a "negotiation", no matter how much you want to spin it.