No, it's not an endangered species, no matter what, in the countries of RSA and Namibia. The White Rhino was brought back from the verge of extinction by game ranchers and international big game hunters in both countries. Lots of $$$ was donated by hunting organizations and groups to encourage and support these projects. There are now a surplus of them and they may be hunted with rifle - very expensive trophy fees - or tranquilizing dart under the supervision of a DVM, in these two countries. The Black Rhino is now starting to be raised as well, although due to its temperament it is quite a bit more difficult. Many other but less well known animals have also been saved in this manner and may now be hunted legally as well.
It was never sport hunting that endangered the Rhino, it was poaching for the animals horn, which is used for dagger handles in middle eastern countries and as an ancient form of "Viagra" in the far east. Rhino was brought to the brink of extinction by poachers.
I darted my Rhino. It was a very challenging hunt, much more intense than a rifle hunt and requiring me to get substantially closer to the animal - under 35 yards, since the dart gun is essentially an air rifle. We had to stalk up on the animal 3 separate times before I was able to get a dart into him. A DVM was in our party and we measured, photographed and implanted a microchip in the animal. An antidote is then administered and the animal is revived and allowed to go about its business. These animals are wild and dangerous; they are not tame nor are they "zoo" animals. Laws dictate how this may be done, who must be present, etc.
There is a Committee on International Trade in Endangered Species (CITES) which makes determinations on the status of all animals and recommends what can and cannot be hunted legally around the world. This includes the legal hunting of Elephant in 5 African countries as well as Rhino in the two countries mentioned above. CITES has the authority to ban hunting of specific animals in countries if regulations and quotas are not met. They also mandate both export and import requirements by all countries.
Hope this provides some educational value and answers your question. I would be glad to book you on a Rhino darting safari, or any other type of hunting safari.