There were some Jews in Satmar, Romania who were lenient about eating dairy made by gentiles. But the Satmar Rebbe cleverly and sweetly put an end to this. One day he announced, “I’m sure everyone here keeps the time honored Jewish custom to eat milchigs on Shavuos. But I’m warning you: by eating gentile-made cheese, you may not be fulfilling the custom. Gentile-made cheese may actually be fleishigs, since it may contain treif fats.” They stopped immediately. (From The Rebbe, The Extraordinary Life and Worldview of Rabbeinu Yoel Teitelbaum, By Rabbi Dovid Meisels page 51)