You counter the facetiousness in a way it stops spreading and possibly even spark a constructive discussion is how I understand it (ESL though). I certainly observed this phenomenon myself (although as the person being facetious, I often feel like "I was joking, I actually agree, that's indeed what I was actually implying, but good you made it clear and explicit I guess")

I guess you'd disarm the person being facecious rather than the facetiousness, like you'd disarm someone about to cast you a magic spell.