re: 'the river' is not allowing marketplace book sellers to list books about Confederacy

This isn't something new. With the stock market the concentration of power into a few companies has leveraged censorship (along with other troublesome things). So in the book industry, if you want to publish, sell, etc. something that goes against the agenda you have to be willing to do it on your own site. You also have to be willing to not be able to do anymore business with the big companies, because they will blacklist you and not sell your stuff or sell to you. So if you want to sell that book on the confederacy and it goes against the agenda you have to be prepared to not have any new books sold to you by the major publishers. This was really notable with stuff related to WWII.