The drug dealers for all the bad they do they also support and help the community a lot. This is part of their strategy, the community in turn protect them, hide them. In many favelas the drug lord is the law, and the law is don't poop where you eat. You may be able to steal from people outside the favela but not inside the favela, if you do the punishment can be medieval, like cut hands or even death. It's not only for residents though. Even as a tourist you are probably safe in a favela, it's their interest you feel safe so you don't feel intimidated to go buy drugs. But again after living in Rio and São Paulo for many years I wouldn't recommend anyone to do that.