They're not "banished". Stormfront is still on the Internet. Gab will be too, at least for a while. They're just going to have to work with companies that don't mind helping white supremacists.
Obviously, these are companies that offer products and they can tailor them anyway they want. But I'm making this as a broader statement about our culture.
What seems to have happened with Gab is that its founder got kicked out of YC for harassing batch-mates, got some publicity for that, and decided to use it to capitalize on the "alt-right". Is there any indication anywhere that Torba is doing anything more interesting than trying to sell neo-Nazis a monorail?