oo! I just remembered a good one (though this is a more gentle one)
back when I worked at a grocery store, I was helping a customer and, naturally, asked how I could help him, so he proceeds to go off on this random rant about how he is divorced, his daughter hates him, his son is bisexual and his ex remarried a rich guy. normally, I would have loved to waste time getting payed to listen to his (mildly entertaining) rant, but I was on closing duty that night and I didn't want to get out late, so I had to cut him off.
me: "Sir, would you go to a therapist and tell them about what type of peanut butter you want/how you want your groceries bagged?"
him: "huh? no"
me: "well, then why are you talking to the grocery store clerk about information a therapist needs to hear? I'm not tryin' to be mean or anything, but I think you're a little mixed up here. this is not my area of expertise XD XD "
fortunately, the guy laughed his ass off (I think was an ENFP actually, he was hella going on an Ne/emo Fi tangent, so naturally he found my gentle yet not-so-subtle Ne/Te bitchslap hilarious)