I'm sorry this is happening to you. It sounds to me like this guy is trying to bully you into rolling over and taking inferior feed. What a jerk. Personally, I would go somewhere else (I know that's not an option for you). Probably the reason nobody else complains is because you are the only one buying the feed. If you see moths in there, it's likely that the feed has been sitting around at least a couple of months. Also, I just read that moth poo accelerates mold growth. Maybe you can ask the manager to complain to the manufacturer or ask him to buy his feed elsewhere.