So he was wrong. VERY wrong but, no big deal. He wasn't acting like an asshole about it IMO. You corrected him and he accepted your much better explanation of water drunk. Maybe give him some neg rep or something but I don't think it was worth any major infraction. Please don't hurt me for sticking up for him, but we all say something wrong at some point. All we know is what we're told, and half of that's a completely wrong.