I work as a Sign Language interpreter. Moral and ethical dilemmas happen all the time. There are books written just on the ethical dilemmas faced by sign language interpreters (like many other professions that are prone to these types of situations)
For the most part, we are usually able to justify most of what we do simply because we are not in fact the perpetrator of the laps in morals/ethics. As an interpreter our ultimate commitment is to provide equal access of communication for all involved.
This can mean interpreting over heard test answers during an exam. Or interpreting what you know to be lies. I have interpreted for people over the phone claiming to be someone else in order to get privileged information. Even interpreted drug deals over the phone.
This is often not a problem when they are simple things like lies and illegal activities. Sure it may conflict with my personal morals, but I know it happens and Deaf people have the right to do those things just like I have the right to do them. So usually simple things like that are easy to justify.
The situations that stick with me, and I’ll never forget are when I’m put in a situation where I have to interpret things that hit much closer to home. Having to interpret homophobic language, racist language, or abusive language. Having to maintain my ethical commitment to stay true to the message, and facilitate communication even though that communication directly comments on who I am.
Sure what I really want to do is stand up, call them an ass (or much harsher words) and storm out of the room/cubical/office/etc. But ethically, I can’t, so I don’t.
Besides that, interpreting is a great job. I love it, and recommend it to anyone willing to make the commitment to become fluent in a culture/language. ;-)