holier-than-thou
From Longman Dictionary of Contemporary Englishholier-than-thouˌholier-than-ˈthou adjective GOOD/MORALshowing that you think you are morally better than other people – used to show disapproval SYN self-righteousExamples from the Corpusholier-than-thou• I know he doesn't smoke or drink but I wish he wasn't so holier-than-thou.• a holier-than-thou attitude• She was intensely irritated by Emma's holier-than-thou attitude.