I do not remember anyone being forced to shop at WalMart and buy their brands?
No they are not -- and that is precisely the problem for Walmart marketing. They're going to end up driving their former customers to other stores to get the things that Walmart has discontinued.
If Walmart hadn't done that, they wouldn't have people starting to "look elsewhere"...
So, you see... that's precisely the problem for Walmart -- people can go elsewhere and that does not benefit Walmart... :-)