In scene 8 of A Streetcar Named Desire, all of Stanley's annoyances about Blanche and her attitude towards him, as well as, all of the insecurities this seems to bring up, comes to a head. He's found out the truth about Blanche's circumstances and the scandalous things she's done. So when Stella criticizes him for eating dinner with his hands and tells him to clear the table and clean himself up, he explodes with all those other feelings and frustrations. He shouts,
"That’s how I’ll clear the table! [He seizes her arm.] Don’t ever talk that way to me! "Pig – Polack – disgusting – vulgar – greasy!" – them kind of words have been on your tongue and your sister’s too much around here! What do you think you two are? A pair of queens? Remember what Huey Long said – "Every Man is a King!" And I am the King around here, so don’t forget it!"
While Stanley has been judgmental and annoyed by Blanche's excessive haughtiness and disdain, it's clear in this scene that her classist attitudes have gotten to him more than he's shown. He particularly hates that Stella seems to be falling into the same pattern of criticizing him that Blanche has. Remember, as a guest in their house, Blanche has been a pretty terrible one. Aside from her constant criticism, she keeps telling Stella to leave him. So when he sees Stella start to look down on him too, he shows the ferocity of a man who is being threatened.