Clerks II turns this into some sort of morality issue. The question is not should you go ass to mouth. The question is why.
Why return to the mouth when the person has opened their ass to you?
Take the Lebanon; forget the Israel. Embrace the ass. Feel the ass. Dig into that asshole. Caress the cheeks with your cheeks. Spread them. Kiss them. Lick them. Squeeze them. Hold them and never let them go.
It really makes no sense to bother with the mouth anymore. Unless, of course, you were 69'n and want to share the taste of each other's ass mixed together. Otherwise, give that ass one final slap and get back to the business of transferring corporate bribes to offshore bank accounts or leaking information about people that dare to disagree with your leader.