The actual expression is "willful carelessness" and is spoken by Norman Gortsby. He's in conversation with a young man who appears to be spinning him a shaggy-dog story about the hotel in which he was planning to stay being demolished (as well as his losing a bar of soap).

The word "willful" means to show deliberate intent, and in using this word, Gortsby is expressing extreme skepticism at the young man's tall story. As far as Gortsby is concerned, this is all starting to smell rather fishy. To lose a hotel and a cake of soap in one afternoon strikes Gortsby as a prime example of deliberate carelessness on the young man's part. Gortsby is a man who prides himself on being able to read people rather well, and he's sure that the young man sitting next to him on the park bench is nothing more than a con artist.

Once Gortsby expresses his skepticism, the young man takes off in a huff. He's either deeply offended that Gortsby doesn't believe him or he's annoyed with himself because his cheeky ruse to get some money out of his mark hasn't succeeded. Either way, once he hears the magic words "willful skepticism," he doesn't hang around to hear what else Gortsby has to say.