First, he didnt hack. The word you're looking for is cheat. Second, he was simply creating a custom texture for his map or whatever, and in the process a stock texture got modified by accident (trust me, this happens when you develop something for dp) and for some reason the mod detection didnt appear.
Sure, give him his 8 ban, since technically he did cheat. I just find it funny that you would want to give him a 32 day ban, as if you would win something.