No advice is going to be valuable here without knowing the full situation. Your design could be full of holes and the coworker is pointing them out, or you coul

No advice is going to be valuable here without knowing the full situation. Your design could be full of holes and the coworker is pointing them out, or you could be in the right and he is just trying to appear knowledgeable. In general, dealing with conflict at work requires a good bit of understanding of human psychology that you cannot condense into a post.