I quite agree with you. I remember being quite embarrassed at one of the lessons of the course I took in Toronto this summer. Our teacher asked us to write a few words on the whiteboard in our first languages. Just for fun. She also said that we were able to write swearwords if we felt like doing so. When me and a friend of mine came up to the board and started thinking about what to write we suddenly found ourselves feeling quite embarrassed. Eventually, we decided to write a couple of swearwords in Russian just for fun. When we wrote them our teacher asked us to pronounce them so she and the rest of the group could practice pronouncing them. It was so funny! I fondly remember Italians and Mexicans swearing in Russian. The funniest thing was that they didn't understand at all that what they were saying was obscene. I believe that the reason why people can easily swear in foreign languages is they don't get that it sounds obscene to most native speakers.