Evidence collector: What's this? [Sniffs box.] Why, this smells like Burke Ramsey's feces!
This is a good point, which I think people are missing. Even if there actually was feces on the candy box and/or pajama bottoms, there's no definitive proof that the source was BR. Wouldn't it be more likely that the source was JBR? The only thing that Kolar bases his theory on is the fact that one item (the pajama bottoms) "appeared too big" for JBR, which is hardly definitive; especially when you consider that she had a tendency to wear long-johns belonging to BR, if the ones she was found in after she had perished were any indication.
Also, perhaps this was the final straw that night for PR.