Why people ask it
Because they have seen lists of them, and because differences between accounts are real and noticeable.
Short answer
Most alleged contradictions are differences rather than denials. A contradiction requires the same claim asserted and denied in the same sense — and a few cases genuinely remain difficult.
Deeper answer
Ask for a specific example first, warmly rather than triumphantly. General claims cannot be examined, and often the person discovers on their own that they are repeating something unchecked. That realization is more valuable than anything you could tell them.
Then run three questions. Is it the same event, or two similar ones? Is it the same purpose — summaries and detailed accounts differ legitimately? And is it a difference or an actual denial? One account mentioning one angel and another mentioning two only conflicts if the first says "only one."
Some cases survive all three questions. Say so. A short list of genuinely hard passages held openly is far more persuasive than a long list you have visibly forced into harmony.
Common mistake
Forcing a strained harmonization. A visibly stretched explanation costs more credibility than admitting the difficulty.
Conversation-ready response
""Which one bothers you most? I would much rather work through a real example together than talk about it in the abstract.""
Source notes coming soon.