No matter how correct you are, you won't get anywhere by making the other person feel stupid.
He gave me this after we went together to a conference on communication and I found the presenter to be making some rather doubtful statements. I asked questions and tried to break the presenter in the QnA session and when I didn't get what I wanted, I left. I was 15 at the time. So, I forgive myself but still cringe hard whenever I remember it.
This advice had and continues to have a really long lasting impact on me (especially in getting me out of my incredibly arrogant stage in life) and my relationships with people. I can still be critical of things while maintaining respect for the other person's context and intelligence. I've found that also helps a lot in disconnecting ego amidst a debate.