I went there in the summer of 1977 on a South America deployment. A work up of sorts before deploying that fall to the Med Sea. RIO wasn't too bad then. Salvador {the city in Brazil not the country named such} was a different story. You had to really watch the street orphans real close or they would slice your ankle open robbing you. They would sneak up from behind and put the knife right at the tendons. I'm talking very young kids single digit age living in the streets with no parents. That's what a moral collapse looks like.
As I’ve understood it, some of the worst danger in Rio now is exactly what you described, crime by street orphans. How sad is that? And, of course, terrifying for a tourist.