Don Lemon’s sexist rant about Nikki Haley on Thursday turned the stomachs of his co-anchors and added to pressure on CNN boss Chris Licht to dump the acid-tongued host, The Post has learned. A furious Poppy Harlow walked off the “CNN This Morning” set following a tense exchange with Lemon after he said the GOP presidential candidate was “not in her prime,” according to sources with knowledge of the situation. One of the sources said Harlow took a “well-timed” bathroom break and was followed into the restroom by co-host Kaitlan Collins — who recently had her own run-in with Lemon....