I don't think these Rhinos are bacteria, so they may not be comparable.
For example:
Cheetahs are a threatened species. Low genetic diversity and resulting poor sperm quality has made breeding and survivorship difficult for cheetahs. Moreover, only about 5% of cheetahs survive to adulthood
That quote is a little misleading. Genetic evidence suggests that cheetahs went through two severe population bottlenecks around 100kya and 12kya, which is likely responsible for much of the low genetic diversity seen in the species today. Their threatened status is not the cause.
Does it matter how they lost genetic diversity? Whether the population bottleneck was caused by the end of the ice age 10K years ago, or by human poachers 10 years ago, this Rhino subspecies is down to 12 vials of eggs/sperm. And even 10,000 years later they are still struggling.
Are humans willing to foster this one Rhino population for 1000 years?
>> Genetic diversity is not a requirement for a species.
It is for any species on the edge of extinction. By definition, they are not adapting. Saddling them with the further burden of inbreeding isn't going to help.
Bacteria can also die in record numbers without much impact. If 1/2 of bacteria "children" die early due to genetic issues, little would change. But mammals invest much more energy into offspring than bacteria. Mortality rates matter.
Bacteria don't even have sex, and while they can pick up DNA from other bacteria via conjugation, it's not necessary for their reproduction.