What was the "sickening comic aspect" of Attitcus' exchange with the small mob of men? What does this show us about the men in the small mob? About Attitcus?

The "sickening comic aspect" was the fact that the men listened to Atticus words but were determined to act regardless. They had enough respect for Atticus to lower their voices, but they didn't have enough respect to leave.

“He is,” we heard Atticus answer, “and he’s asleep. Don’t wake him up.”

In obedience to my father, there followed what I later realized was a sickeningly comic aspect of an unfunny situation: the men talked in near-whispers.