I see the conscience argument as people wanting to have their cake and eat it, too. They want to practice a profession, but be able to pull out a conscience card that allows them to act unprofessionally when it suits them. One of the ethical tenets of health care professionalism is that of patient autonomy. We do not impose our personal beliefs on our patients. We are engaged to help them achieve their goals for themselves, not what we think their goals for themselves ought to be, taking into account the generally recognized standards of care, etc.
No one is bound and obligated to behave in a way that violates their conscience. They are free to leave the profession if they cannot conscientiously fulfill their duties, and that would be the course of someone who really had the moral high ground. But people who want to refuse to fulfill their duties without consequence simply don't have sincere courage of commitment. They want to exercise their prejudices without bearing any personal cost, to continue to enjoy the benefits and privileges of professional practice despite failing to uphold the ethical standards of the profession.
You don't want to dispense legally prescribed drugs because you are opposed to the use to which they will be put? Very well. I applaud your strong conscience. Quit your job and go work in another industry. Freedom doesn't mean getting everything you want. It means that you are able to make decisions and face their consequences... just as you are so eager to tell others to do.