Bottom line is: the notion of "sacredness of life" stemmed from simple self-interest.
Just look how very selective we are with this whole "life is sacred" business. One just needs to look in his salad bowl and his hamburger. Your very body is evolved to kill life (bacteria) with each breath you take.

While i don't believe in any objective value of life, i do realize that we all have certain common interests, namely to survive and be happy. I try to respect these interests.
However, when i have reason to believe that a sacrifice can bring much more overall happiness, I would carry through with it.

PS: not saying we should invade Ugada or anything - I think there are better ways to bring change about.