I was uncomfortable, but not in the way you'd expect. The carnage on display, as the film implies, is strictly language.
CARNAGE captures what it's like to be the uninvolved 3rd party witnessing a passionate disagreement, which turns from very circumstantial (a playground fight between children) to very personal. It's the equivalent of stoking a small fire, that fire being in a roomy apartment no party can seem to escape.
I must have said the words "we have to go," speaking on behalf of the two couples, out loud at least 3 times. Nerve racking, to be sure, even if it's worth a few laughs. John C. Reilly shines, but that's nothing new.