I agree – it comes down to mutual respect. We tend to personally identify with our ideas – they become part of who we are. To attack someone’s idea can be perceived as a personal attack, and when we feel that is what’s happening, it becomes more important to defend self than to try to be objective. When instead we find common ground we are validating the person, there’s no need to defend against someone who is agreeing with you, and the door opens for a more positive discussion. Thanks for your thoughtful comment!