I assume since you don't know the gender that this is a unisex bathroom. If this is the case, no one's masculinity would be threatened if you strategically placed a large bowl of popouri, a sack of matches (for the sulphur kill), a few votive candles and a big can of Lysol Disinfectant in there. The whole ambiance of the bathroom would change too. A feminine touch might make it uncomfortable enough for a man to poo.

I always thought human waste smelled a lot worse than dog poo. Dog diets are simple: dog food. Whereas god knows what weird zebra crap people eat any given day.