Lying

One of the easiest things in the world is to lie and pass one as someone else. If the interaction is brief enough and if the other person is not paying too much attention/significance to the interaction then any person with even an iota of IQ can also get away with it. However just because one can do it, should you do it?
Over the past 1 month or so, I have spent 20-30 hours over phone trying to coach a kid on CAT interviews. He wants to pursue MBA because he intends to use those skills to get into healthcare management, where he believes he can contribute significantly and get a lot of satisfaction. However being an engineer from an unrelated field, he wasn’t sounding very convincing in the mock interviews. Hence he was literally pressurized and forced to change the storyline of “Why MBA” to finance where he seems more natural and presentable. He says just because “I am good at something that does not mean I want to pursue it as a career. Healthcare might not be the most glamorous of the sectors (relatively speaking), but then with my qualifications and dedication I am sure I will never have problems of bringing food to the table.”
IIM Interviews are a chance for which many people would be ready to kill for. During interviews and discussions where one is being evaluated, everyone blemishes the facts or is economical with the truth. However just because everyone lies, does not mean that he should also become phony. I am not questioning the moral or ethical standards because I believe they tend to change/evolve with time and based on the context. What I am asking is that if the stakes are too high, then is it ok to let go of one’s beliefs and conviction in order to make a favorable impression?
PS: He went with the finance story.