We tried "Defecate" once, but it just made combat stinkier. Forcing those in the party with low constitutions to save versus poison or vomit. A party member died because at that time, if a blow was struck while a target was incapacitated, then it was instantly death.
The same way you don't get an armor save if you're tied up and someone slits your throat.
Our DM was unforgiving if we tried to get clever. I do wonder what the result if the masturbate command would have been. I could see ol' Frank Wilson give a crude cackle and either allow it because of low brow creativity, or come up with an equally yet horrendous backfire to the plan, like a poorly worded Wish spell.