The apologetics study group LOVES this quote from Groothuis' Christian Apologetics: "We may be entitled to our own opinions, but we are not entitled to our own facts." p. 124 It's actually a variant of a quote commonly attributed to Daniel Patrick Moynihan and a couple others, but that is not credited in the book. Still--it is true. I think it is fair to say it has achieved meme-status.
"'Adultery is wrong' is true because that statement corresponds to the objective, universal and absolute moral law revealed by God, which is in accordance with his eternally stable character and the character of his creation." p. 126
That last quote hits on natural law, divine command, Euthyphro's Dilemma, the is-ought fallacy, et cetera. I am currently discussing that with some folks from ILP here, and have done some work on it previously if you scroll to the relevant section here (“Euthyphro, Hume, Plato, Gettier”).