Acametis already hit on this pretty well, but yeah, if every AI adopts Emancipation as soon as they can, it makes it very hard for the player not to. The devs did little tricks like this all over the game rather than actually coding a competent AI. I'm sure it's cheaper and easier to code hurdles for the human instead of a smarter AI. In a perfect world, Deity would get no bonuses, but the AI would just be better at the game. But that's not the case unfortunately. The same military tricks that work against the AI at Settler level will work at Deity as well. The task is to get your empire to a point where you can exploit those weaknesses in the first place.