Look, if you really feel ashamed for doing what we do and for making the money we do, then quit. This is by no means my dream job but I enjoy calling on my customers. We make a good living and have good benefits and are able to take care of our families and that's what our main job is!
I don't do this job for BMS, I do it so my family is taken care of so my kids can go to college and then themselves lead a good life. If this job gives me the ability to do that then so be it.
I see no reason to feel guilty for doing this job. As was said above, most doctors do want companies developing new meds to take care of their patients and are appreciative when we are able to help with samples.
I love the hypocrisy of people that say they feel guilty but continue to work this job and make the money they do. If you TRULY feel guilty then you wouldn't be doing this job! Look, God knows there are PLENTY of reps out of work that would take your job in a minute so if you really feel this way then leave and give someone a chance that wants to do the job and stop bitching about it and do something!