How do you explain why to this?

Kind of gross...sorry....that's how three year old boys roll...

Kenson loudly passed gas today and muttered something about pooping in his pants. He then said, "Wait a minute! Let me check!" and started pulling down his pants and doing something funky with his hand and bottom. I quickly said something about if you have to check, you need to go the bathroom and try going poop, that we don't put our hands in our bottom to check for poop. To which he replied the ever famous three year old mantra, "WHY?"