I never said that it would make everyone get along and make disagreements and anamosity a thing of the past. Where did you get that from? I did not write this.
The topic of the post is if you could erase one thing from the world what would it be? Greed, prejudice, sickness were but a few examples given of sources of human suffering, and all of them valid, removing them from the world would not solve all our problems, but it would certainly be a good thing and make the world a better place, and if we evolved as people past the primative instinct that might makes right then this would also be a step forward. If we found the cure for cancer there would still be strife in the world, but it would obviously be a good thing. Let's not turn a positive thread into something negative.
Yes, you could still hurt people in a world that is nonviolent. Stopping a war for example doesn't remove the underlying political conflict between two nations, but invading, bombing and shooting down eachother is the ultimate manifestation of that conflict, and avoiding this would certainly be a better outcome. Nothing is more final than death, i'm afraid that you can't "hurt someone way worse" than killing them.