I honestly didn't believe that there were rules on what enemies/allies were. That rule changes the whole feel of this game imo. Everyone who isn't fighting with you against whatever you are fighting is an enemy.
Thats... quite dogmatic.
I don't see how this is "dogmatic"... and I think you are reading too much into things.
This doesn't mean the world is out to get you, they are simply definitions of scope of effect. It even says that the enemy does not need to be "hostile" to you, but rather an "enemy" is just a term meaning that they aren't your ally.
The use of "enemies" in 4E simply is a mechanic to allow you to give immunity to your allies. When this immunity is not granted, then "creatures" encompasses all. Affecting only "enemies" is really an *advantage* to a power.