Not all abused children turn into monsters, of course; however, some very good researchers including Dorothy Otnow Lewis, James Garbarino, and more have found that when they look close enough they find far more serious abuse to those that turn out to be monster. Unfortunately traditional media doesn't cover this and often misrepresents the facts.
However, even if this is in doubt there should be no excuse for declining to protect children from child abuse when ever possible.