There is nothing stopping you from buying an android phone. It is a viable alternative with greater marketshare.Saying Walmart shouldn't sell goods is just avoiding the question.
There is nothing stopping people from shopping at Target or any other store. Walmart doesn't take a 30% cut either.
You know there is a problem when Walmart treats their suppliers better than you.
The real question is whether Apple can legally ban apps that “replicate features” Apple provides or sells. Honestly that policy may be the only one that is anti-competitive by the FTC standard and its easy enough to change if forced to.