I can sniff you, but you can't sniff me

This is what Jon always tell Max. And if Max insists on doing sniffing his butt, he gets a snap from Jon. So Max has to resort to opportunistic methods to sniff Jon. The only time the opportunity arises is when, during their twice daily walks,  Jon pees and poos. Jon will be in full concentration of eliminating that he just ignores what's happening behind him for that short moment. Sniffing Jon when he pees seems acceptable from my point of observation, but sniffing when he poos? That is disgusting, Max.