When should someone feel obligated to reply to someone else?

Should we if they ask us for a reason of a hope that is in us? Should we if they are seeking to better understand how to stand by the Creator and we have personal knowledge that can help them do that? What if it would be in the course of a vain debate or we think directly answering what they ask will do more harm than good? What if it is someone who is a very outspoken enemy of the Creator or a demonic spirit? Is there…