What do Christians mean when they implore you to have an open mind? I can assure you that they do not mean the same thing that is meant when the non-religious say it.
Atheists, humanists, agnostics, and the non-religious mean for you to keep your mind open to new ideas, new information, without dismissing it outright. They mean for you to examine the evidence and determine its validity. They mean for you to research the idea or information yourself and find its truthfulness or falseness.
Christians mean for you to make your mind receptive, pliable. They desire that you suspend rational thinking and instead let your emotions make your decisions. They want you to accept what they are saying without resistance, without question, totally on feeling. Finally, they want you to realize the truth they are speaking, that they are right, and then you are to convert. That final step is what they had in mind all along. They are not arguing the point and are not receptive to anything you have to say. When it is all over and you haven’t converted they turn and walk away dismayed that you have rejected the truth. Their idea of compromise is that you give in.
Debate is useless except for the sake of those who are freshly converted or have doubts at the beginning. Unless they are the ones you are arguing with, the not quite set in the flock breed, or unless there are some in the audience of that type, why waste the time.