I'm afraid I have just given this quite a lot of thought. Although I am unable to calculate the terminal velocity of a poo I doubt it would be much more than 100 mph, but then again, at that height it might be quicker due to lower pressure at height and would therefore slow down as it reaches the earth. This leads to other questions like "how aerodynamic is the poo?", "what percentage is the water content and therefore what is the consequent mass of the turd?". Either way, it would make a splat, and would possibly hurt depending on consistency.
Have I thought about this too much?
If he has had a curry I doubt the consistency will be firm