Here's a fascinating question to mull over -- call it an exercise in future history:
What are the ideas or practices that are uncontroversial and widely accepted today — and that you personally find unobjectionable — that you think might be seen as barbaric or immoral one hundred years from now?
I suspect many, drawing on our history of miscegenation laws, will put the current practice of denying marriage to gay couples at the top of the list. My best guess (and based on the provision that it be something I personally find unobjectionable): Eating meat. As protein substitutes become tastier, more nutritious and cheaper, enough people will stop consuming "burnt, dead animals," to paraphrase Arlo Guthrie, that our descendants might well be horrified at us.
I don't think we'll ever get rid of tobacco, alcohol and other drugs -- using foreign substances as a crutch against reality has always been a part of human nature and always will be. I wouldn't go so far as to predict widespread acceptance of such weakness, but it does look like marijuana is on the path to join alcohol as an OK way to bend our perceptions.