Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) said: "When you see a man calling out with the rallying cry of the Jahiliyyah, shame him (by plainly naming his father's private parts) and do not use euphemism."
Hadith Referenceالمعجم الكبير للطبراني / باب الألف / 529