Conflict and disagreement are different.
Two people can disagree on which soup is their favourite. They can happily discuss why they think so without conflict.
Ridding the world of sadness would be a personal effect. We would have no (theoretically) suicide, depression, etc. The world would be a happier place.
Ridding the world of conflict would be an effect on human society. No, this does not get rid of disagreeing on things and simply discussing them. It gets rid of violence, wars, fights, expressed anger, etc.