*A argument, not one that would hold in court. IANAL.
EDIT: It seems I misunderstood Amazon's lack of Chromecast support. I hadn't thought of trying to buy Chromecast through Amazon before. I own three of them and bought all through the Google store.
There are exceptions to "sell anything", but chromecast and apple tv are the only business exceptions, not based on safety/legallity/ authenticity etc.
I don't think there is any argument that passes the sniff test for them not to be able to sell a physical device like chromecast from amazon.com. The level of incremental work is basically zero to add an item into the store.
That IS pretty much directly comparable.
I suppose the difference between this and Walmart's move is that we are not entitled to buy the things we want from every shop, whereas these drivers are probably entitled to employment without discrimination in regards to other customers they provide services to?