Letting the unaffiliated mobs do it instead will be of scant comfort to the people who will get killed. The Government will certainly protect the mobs from retaliation by the victim's families.
You could make the argument that Baltimore is dangerous. You're on your own if you decide to go in the city by yourself.
These South Africans didn't go into "Baltimore", they were born there. Yes, anyone going to South Africa right now is a fool, but people can hardly be blamed for the situation into which they were born.
I believe I have read they have enclaves, but I have little doubt the government would use whatever force was at its disposal if these enclaves attempted to repel the mobs by force.
Seems like the South African Government is weak.
Otherwise, private military companies and security firms will be banned in South Africa. But apparently that's not the case.