Evidentally the BBC does periodic studies on what expletives are most offensive to the viewing public, and the general view of broadcasting offensive language. The most recent report (in .pdf format) is here. (warning: by nature there are a lot of non-Hatrack-approved words).
While the most offensive terms still seem to center around slang for sexual terms, the groups with the biggest increases in relative offensiveness over the past 9 years are those dealing with racial and minority groups. Words offensive to Christians, Jews and other theists tend to poll as the least offensive (cf Table 1 on page 13).