A phrase used by comic BillEngvall in describing the proper address of those people who are so stupid that the people they encounter ought to have some kind of warning that they're dealing with someone stupid.

The quote is something like:
* Stupid people should have to wear signs that just say, "I'm Stupid"

The routine (first time I heard it) began with the words, "I hate stupid people ..." and went on from there to illuminate the topic with examples of the kind of too-big-to-ignore things that stupid people do and say.

My family and I will, on occasion, encounter a fugitive from one of Bill's sketches and, with a glance at each other, recite "here's your sign."

-- GarryHamilton