It's not that weird. With a FOSS license, I know I can use a program for anything I choose to and the terms will never change. I might launch a startup with a friend tomorrow using a package and complying with its license terms, and a million dollars later we're still legally entitled to use it.

Adding constraints later is a non-fallacious slippery slope. The restrictions Redis added aren't directly onerous to 99.999% of users, but now the world is divided into people who are allowed to use it at will, and people who can only use it in certain ways (or not at all). That's an enormous change from a FOSS license. And if they change it today specifically to lock out Amazon, will they change it again tomorrow to lock out my startup? The thing is, now that they've established precedent, there's no way of knowing what'll happen later.

Again, I know I can use GPL or MIT or BSD software for anything I want as long as I play by the exact same rules as everyone else. There's nothing that says you can use it but I can't. The difference between Free to non-Free is vast, even when I'm not affected (yet).