Has Dean gone too far?

I understand the whole "there ain't no me if there ain't no you". I understand the emotional trauma Dean has to deal with loosing his brother again and again. But since the end of Season 8. I keep wondering if he's gone too far to protect Sam from death even if it means lying to Sam and denying Sam's very own free will. And the idea that a big part of Dean is protecting Sam only because he fears for himself starts creeping up into my head, because if Dean truly loved Sam, he would let him go as a hero than become a vessel to an angel or demon. I'm starting to wonder if he fears the loneliness so much that he would rather die than have his only brother die and leave him alone. We all glad that Sam's alive, but if Metatron's scheme to banish all angels from Heaven failed and the world did not have to deal with million of angry fallen angels, then Dean just chose to sacrifice the world in the name of his brother even when it means his brother will continue to suffer. This whole idea makes me depressed but I could be only looking at the darker angle.