Oh yeah, the humans are great at that! ...oh wait. 
No they aren't. But why would I support the Elves in commiting the same atrocities to humans? And why would the multitude of human nations in Thedas allow the Elves to mistreat their fellow humans?
Again, where does it state elves have to be some kind of fantasy hippies that strive for equality for all? Humanity has held its boot on the throat of elvenkind of thedas for a long time. At this point humanity should be thankful if they only lose the foot in the boot. I seriously doubt that the elves would allow any kind of permanent human residency within their borders.
You honestly think that the Elves even pose a threat to humanity? Have you been out in the sun too long? If humanity wanted to, they could obliterate the Elves. It is the Elves who should be thankful that they still live.
The entire point of an elven kingdom is that the elves have self-determination over their own future, not to leave them at the mercy of humans who view them as (in Duncan's words) "less than people". We've seen what happens to elves under human rule - whether it's the purge in the Denerim Alienage that left countless dead, including children in the orphanage, or the massacre of thousands of elves in Halamshiral because Celene didn't want to appear weak - and I think an alternative is in order where the elves are masters of their destiny.
So in the name of the inequality the Elves suffer, they will bring even more inequality to the table! And you can drop the rethoric of a twelve year old, and stop listing events that you think helps your pathos. It only makes you seem even more pretentious.
At the same time an elf could become king of a human nation.
I would love nothing more. However after a few generations it would probably be a human again. Unless the Elven king would try to go all "racial purity madness", in which case he would probably be disposed off again soon.
Do you also object to the fact that this is true for every nation that currently exists in Thedas? Can a human become king of Orzammar? Can a Qunari become ruler of Orlais?
Yes? Why wouldn't I? I object to feudalism in general.