You have a choice. Don't use the other store. If there was only one AppStore for games on PC you'd have no choice. That's the point. If it was only Steam, and Steam said they won't allow any games that depict war, what choice would you have?
But that's the magic of having multiple App Stores, they have to compete. They can't be the world police of software.
What's so hard to understand that having a choice means you can choose to do something, or not.
If you want to use your phone with only Apple's Appstore, continue to do so, if an app you really want is not on the app store, then DONT BUY IT, except now, someone besides you has the CHOICE to download it.