"If you refuse to utter them, the group will not accept you as a member, you will fail to infiltrate them, their planned terrorist attack will not be discovered in time, and innocent people will be murdered in an attack on the minorities the slurs target."

Valid point overall. But the problem with undercover agents infiltrating terrorists are not really racial slurs. To be accepted among real terrorists, one has to do real terrorism.

(book recommendation: The Little Drummer Girl by John le Carré)