I was about to ask the same...
me too !!???
Maybe he 'll get pregnant!! LOL (≧∀≦)
They're worried about an upset stomach, diarrhea etc
Leaving semen in a rectum can cause upset stomach, and an infection that can affect other parts of the body especially the gastrointestinal system. That's why it's important to get it all out.
Hahahaha! That would be great! That's more Sex Pistols though xD
Ohhh well... you learn something new everyday =(^_^)=
Wait, what? What is going to happen to his stomach... and why? ヽ(`Д´)ﾉ