Removal of many useless species would be a boon for mankind. Take the whale: whales, which we don't eat, swallow plankton, krill and small fish - by the million, reducing the amount of food for other fish which we do eat. Fewer whales = more food for man.
Tigers: we no longer need their fur to keep us warm. They kill prey which we could eat. Same argument.
I've yet to find anyone who has a rational reason for preserving elephants, rhinos or pandas.
Now, polar bears: they're useful; they eat seals which otherwise would eat fish that we can eat.
Get the drift? We live in a world where millions are starving. Letting many of these predators become extinct would save lives. I'll take that against preservation for preservation's sake any day.