Tell him how much you appreciate it. Tell him you need people to tell you no, because it helps you get to the yes quicker. It'll blow him away. Humor is one of the most important communication strengths needed to master in the selling process. If you can get the prospect or customer to laugh, you can get him to buy.
Nothing builds rapport faster than humor.
It brings the selling process to a real level. It brings out the truth. I have found that many truths are revealed through humor. The earlier you get a prospect to laugh, the better. Laughter is a form of approval.