I think Carlson actually could come up as a question if they have run out of ideas because:
-He represents the behaviour of typical ranch workers.
-He is unaware of Candy's emotional suffering when he is intent on having his dog killed.
-He first suggests that Candy should shoot his own dog before he goes on to say that he can kill it himself
-Slim feels the need to remind him to take a shovel because he is so emotionally unaware that he might not have even buried the dog after shooting it.
-He does not understand George's behaviour after shooting his best friend. The final line undercuts the sad moment with the brutal reality of life on a ranch and the emotionless working environment.
-So Carlson shows the emotional oblivion that comes with loneliness as a typical ranch worker. His treatment towards Candy's dog shows that the natural world does not allow for friendship, dreams or vulnerabilities. His power shows how, in reality, the weak are preyed upon.