Yes, lasers should be banned on the battlefield, because it is an inhumane war practice. There are a great deal of problems with hurting other people as much as possible, including that governments and human rights groups have to deal with the many soldiers who are now surviving wars. Lasers are extremely destructive, and governments should find other ways to make their points.
In theory, using lasers in combat situations (if they were weaponized) would be more accurate. Stray shots and collateral damage would theoretically not be possible. That is, if we're talking about using lasers as a way of dealing damage and not just for secondary purposes like targeting and so forth.