That's sarcasm, but I actually think incongruously lighthearted music is captivating.
Can you think of some examples of incongruously lighthearted music accompanying a brutal attack? The "Singin' in the Rain" scene in "Clockwork Orange" comes to mind.
But come on, Jon Huntsman on Mitt Romney is a far cry from ultraviolence.
AND: As for whistling and violence... don't forget "M"!