"as long as it does not involve the mistreatment of the animal, and sustainability is managed then why not?"
True, however what is happening goes against both of those principles, the whales essentially suffocate and as far as sustainability goes for the minke whale it takes about 7 or so years to reach sexual maturity and birth only happens about 2 years, when you also factor in the survival rates of calves (killer whales etc) it leaves the populations more vulnerable to collapse
