The most important reason for relying on evidence during a discussion is to support your claim.
In a discussion, the most important thing is to basely generate your claims through arguments that support and give your ideas a solid and strong foundation. The most important thing in a discussion is not to win, but to support your claims on valid, true, current, and well-structured arguments. This way you stand up for your ideas cohesively and give your discussion a tone of credibility and show that you have knowledge and priority over what you are talking about.
