I'll just say it. It may have been an exceptionally good day for him, or you may have been experiencing an exceptionally bad day, but the time I met him at a convention, Manu Intiraymi was very nice and approachable, and pleasant to chat with.
I personally do NOT get autographs, and I only like to chat with the guests. Never once did Manu make me feel like I was pressured to buy an autograph. Perhaps this was after your experience and he gained some experience.