what is Carlson's problem and what solution does he suggest?

Carlson is upset that Candy's old dog smells in the bunkhouse. Carlson claims that Candy's dog is old and useless. He says Candy is doing the dog no good by keeping it alive. Carlson pulls out his Luger gun and offers to shoot Candy's dog in a way that causes the dog no pain. Slim agrees and Carlson takes Candy's dog out into the night.