I have two similar encounters in the last few years.
Both of the “I will speak Spanish, and “You, Gringo will have to learn it!” went broke shortly after my confrontations.
Both were shops where they altered clothing, drapes and even sewed from scratch items.
A Mongolian Sister combo, who speak great English, bought one of the shops, and the really nasty one went out of business.
I wonder if most people realize “Gringo” is not a compliment but a slur.