The worst and the stupidest kind of opinion is that asserting anti-whaling because whales are inteligent mammals. No IWC (International Whaling Commission) members or any other official organizations isn't arguing from this point of view. But voices of mass medias and NGOs of anti-whaling countries has arose public opinion, and lots of people still blindly believe this.
Judging its cluelty by their inteligence is very dangerous opinion. These people really believes that there is no problem killing HUMAN if they are less inteligent. And furthermore, having big brain like whales doesn't actually mean that they are inteligent. If the size of their brain is in proportion to their inteligence, they must be a lot smarter than human beings.
assert : 強く主張する mammal : 哺乳類 IWC (International Whaling Commission) : 国際捕鯨委員会 be in proportion to - : ～に比例して