This may be his version of 'tantrum/aggression'.Repetitiveness seems to be an issue in autism as well.He may have unwittingly formed a repetitive behavior associated with the response he received initially?Perhaps its reaction,was fulfilling in that it seemed to accomplish some control of affect towards you and became a method of rebellion.Because repetition,compulsive tendencies,ritualistic behavior,sensation seeking,GI issues,and a lack of ability to empathize are all associated with his disorder any of them seem like factors,and could be contributory.There is also the thought that he may feel a level of 'control' in being able to manipulate a response with this behavior/function.This is all not uncommon,if you google autism and defecation behavior you will discover that the behavior and the dx are associated enough to pull up a lot of different posts.Tbh I know nothing personally about the dx,but upon looking it up,that was what I saw in reference to the behavior and disorder.Your handling of it is very loving and impressive.It seems to go w/o saying that you are a very loving,wise,and balanced mother,and are doing an excellent job as such.He is very blessed to have such a mother.~hugs~ W