If we lack the training and memorization necessary to give a wonderfully complex answer, we may just opt to change the subject. Our silence surrenders to the wimpy relativism of the campus mind, and our inquirer walks away unaffected. One reason is that the ground rules of belief have changed over the last thirty years. The perceived nature of truth has become more fluid and personalized, rather than unchanging and absolute. Students view truth as being like jello, conforming to any new idea that captures it.
Personal taste is the ultimate measure for validity.
I think we can. But we need to communicate that truth in ways that appeal to the experience of the people around us. A recent news story may give us some clues. The story amazed me. A year earlier, a drunk driver had run down a woman on a sidewalk.