It would depend on the situation.
If they’re knocking on my door, I personally would entertain the conversation long enough to learn something, and then maybe teach in return. Depending on how much time I have for a discussion, I’d ask them to elaborate on the points they are making, then invite them to read Scripture with me in order to see if the Bible really means what they’re saying it’s meaning.
If it’s on the street, I’d politely tell them that I have somewhere to be and can’t entertain a discussion.
If it’s at the coffee shop, then I’ll happily talk with them all day if they want. That’s what I’m there for.