Some species of Rhinos had become almost extinct. In fact one group was thought to already be extinct, when a group was discovered and relocated to a protected area. They are making a comeback in protected areas. Regulated hunting is a means of animal population management. I have no problem with REGULATED hunting.
And there is the answer. In areas with regulated Hunting, Hunters pay large sums to local tribesmen for the safari. Also Rhino come with huge trophy fees such as $500,000 or more. In many areas, the trophy fees are split between the tribe and the government. A poacher can get $50 for a Rhino horn, (and feed his family for three months.) When tribes are getting 200K+ for a Rhino, you can bet Rhino's are well protected. Like I heard one Namibia official put it, "You will never find a poacher in Namibia." I take that to mean, if one would attempt to poach there, they will end up in an unmarked shallow grave.