What are Carlson's reasons for shooting Candy's dog?

Carlson's reasons for shooting Candy's dog are that the dog stinks, has no teeth, suffers from rheumatism, and isn't good for anything.

"Well, I can't stand him in here," said Carlson. "That stink hangs around even after he's gone." He walked over with his heavy-legged stride and looked down at the dog.

"Got no teeth," he said. "He's all stiff with rheumatism. He ain't no good to you, Candy. An' he ain't no good to himself. Why'n't you shoot him, Candy?"