The reason people are incensed about FAANGMP doing so is because, in their respective markets, they're monopolies.
No one would care if Google banning a developer meant they could list their app through a non-Play app store with decent exposure, or a non-App Store at all.
But that's not the reality we live in.
So it's more like if Walmart moved into my podunk town, put all the local shops out of business, and then banned me.