The logical fallacy of argumentum ad lapidem occurs when someone dismisses a statement as absurd without giving proof of its absurdity.
Rocky: "God created the Heavens and the Earth in six days."
Sandy: "It is absurd to say that God did it. Christians are constantly saying, "God did it," which is irrational."
Rocky: "How so?"
Sandy: "Don't so be silly."
Rocky: "By revelation, I know that God created the Heavens and the Earth in six days. In other words, God speaks to me through the Bible and shows me that this is true. Through observational science, He shows me that there are no contradictions but only confirmations."
Sandy: "It is ridiculous to claim that God revealed this to you."
Rocky: "What makes you think so?"
Sandy: "I have to laugh because that is so stupid."