I catch one of my students cursing on the phone, in an obscene manner, and presumably about me. In my experience, there is one sure fire way to cure this deplorable behavior- I drag his sorry ass to the nearest bathroom and wash his mouth out with a bar of soap. I make sure his tongue gets good and lathered with the soap, as I jam it in and out of his mouth. This will teach him to watch what comes out of his mouth.