While it may seem counter intuitive, SANCTIONED and licensed hunts (not killings by poachers or local villagers) can strengthen a herd and more importantly bring money in for conservation.
Many animals in Africa are on limited resources on limited land. If their numbers tax their resources the animals will either starve, or they will go out side of their protected areas and encroach on farmland. While I confess I don’t know as much about the black rhino, elephants and lions are often killed, usually by poison, by villagers.
A sanctioned hunt to take out an older male will not hurt the population. A cull will free up resources for the females and younger, more viable males. And probably the most important thing is the money goes to the conservation efforts. Those protected lands are woefully underfunded. They need rangers to patrol for poachers, money for local education on conservation, and paying farmers for lost crops or cattle instead of them going after the animals.
In a perfect world someone rich would give a fuck or two and fund these efforts properly. Or maybe Africa could advance enough economically to fund these projects by itself. But it isn’t a perfect world, and something like these hunts is a decent way to get funding and awareness.
Extinction is nothing new. Animals have been coming and going since their inception. The earth has seen some massive extinction events in the past. With the probable coming climate change, I would expect more extinctions as some species fail to adapt, and others are unable to migrate to more suitable climes. We are used to seeing the world as static, but it has never been so. Remember the Sahara was a jungle not that long ago.