aside from being uncomfortable with the way your question is posed (the assumption of a single set of ethics, the assumption of nonviolence and justice, or anything else, as unequivocal goods, and the assumption that ethics are the most significant factor in maintaining a society), just taking the final question as an interesting jumping off point is pretty huge.
i don't anticipate a nonviolent future. i want a world where violence is more human-sized. where fists are more likely than guns, for example, and there are no bombs from above. what keeps us from doing that today? an entire cultural mechanism that tells us that the police and the justice system are the (re)solvers of conflict.
i'd like a world where there is actual diversity, instead of rainbow colors shellacked on a monoculture. what keeps us from doing that today? the well-known culprits of sexism, homophobia, etc, but also binary thinking in general, cultural appropriation, and of course, most significantly genocide, including not just killing entire cultural groups, but removing them from their culture and vice versa (think stealing indian children and schooling them far from home, language disintegration, english only laws, etc).
in other words, your last question assumes that ethics are a thing that individuals can effectively change on our own. (depending on how you define ethics, that's of course true. but that level of individual ethics has been pretty much proven to be irrelevant to world-change.)