I don’t mind if they shoot them but it would be because they are destroying the environment by competing with native species, NOT because of their farts.
I mostly agree with you. If you were managing the deer population, or the bear population, the fish or any population that was not privately-owned, you’d want to find the point where ALL the costs were balanced against ALL the benefits. So, the emission of greenhouses gases might be part of it. But, only a small part. Mostly, we like bio-diversity. We view the entire world as a zoo in which we can enjoy not simply seeing various life forms in isolation, but in their habitats, and as parts of bio-systems. This is a little tricky as, for example, we don’t want bears roaming off their reservations onto nearby ranches and towns. But, there’s no big problem with deer roaming a bit. So, how many permits should you issue for hunting camels? Maybe a lot. Indeed, instead of charging people to hunt camel, maybe you should pay them. By adjusting the price, we should be able to maintain or even enhance bio-diversity in the world, which, as you point out, sometimes means culling some populations in order to preserve space for other populations.