A means to put the weight of the action back on the person questioning it to begin with. By asserting you have a Cold Soul, you are suggesting you are soulless and therefore can't empathize with their plight. Instead of merely justifying or deflecting your actions through dismissiveness, your putting the burden of reason back on the accuser. Your asking them to examine the severity of the action they deem intolerable, and doing it in the contextual framework of soullessness.
After the movie is over, some patrons approach you and say your loud, crunching sounds were quite rude and distracting.
Your response: I guess I just have a Cold Soul.