EXCLUSIVE

KFC ﻿is clucking pissed about an anti-Hillary Clinton button comparing her to one of the Colonel's combo meals ... TMZ has learned.

A blatantly insulting pin is making the rounds at the RNC with the slogan, "KFC Hillary Special: 2 Fat Thighs, 2 Small Breasts ... Left Wing."

A KFC spokesperson tells us they had nothing to do with the production of the button, and further ... the company "does not endorse any political candidate and certainly does not support offensive, derogatory portrayals of any person."

Aside from the obvious misogynistic shot at Hillary ... the rep thinks the button also disparages KFC, and is an infringement of its trademark.