These decisions are not made lightly, and (as contradictory as it sounds) are often made by people who care deeply about the welfare of these animals. Walrus attacks, while incredibly, incredibly infrequent, are not unheard of and can be fatal - in 2016 a tourist taking a selfie with a walrus in Asia was dragged into the water, held under and drowned. This is the scenario, I imagine, they were looking to avoid.
If humans begin to perceive animals as a threat, the results to populations can be devastating. For example, somewhere in the region of 400+ snow leopards are killed by humans annually, many in retaliation for livestock predation.
