Revisionism with some sloppy relativism mixed in. For you to believe your argument, you must honestly believe that at some point in the future, it will be secularly moral to remove rights for gays, remove property rights from racial Jews, enslave blacks, and conquer, kill, and rape.

The truth is that nobody believed it was morally right to keep slaves who wasn't benefiting from it and using your type of relativism to sloppily justify it to themselves.