I believe that many commenters here interpreted Harris uncharitably. He is not giving himself more reasons to not change his mind. He is not interested in an independent judge deciding who is right. He seems to want to genuinely figure out whether he is missing anything important -- to him! Not to other people. That's why he goes into a lot of effort to list, steelman and address all previously made arguments he can think of. If you think you have found an argument he did not bring up, he would likely be interested in hearing it. If you think that you have found an issue with his steelmanning attempt of an existing argument, he would likely be interested in hearing it.