One time I was talking with my neighbors who lived on either side. One neighbor used the expression "Jew him down" and then said, "Oh, you're not Jewish, are you?" The other neighbor, who I knew was Jewish, didn't say anything, but left. Neighbor 1 said he didn't mean it as any kind of insult, and in fact he learned it from a Jewish guy. I had a long talk with him about why you don't say stuff like this, even in casual conversation, even when you don't mean it as an insult. He went and apologized to the other neighbor, but I am sure the damage was done. I don't know how he got to be 30 or so without learning this.