The classical thinkers (Plato, Aristotle, Dionysis the Areopagite) are the fathers of western culture and they had something to say on this.
They argued that an act isn't good unless it's good in all respects, from the intention, the means of achieving it and the consequences of the act themselves. If any part of the act isn't good, then the outcome cannot be justified.
This is known as 'the ends do not justify the means.' An act and its consequences aren't virtuous unless the means are themselves good and virtuous.
A modern example is the argument over the ethics of the bombings of Nagasaki and Hiroshima in 1945. The acts ended the war in the Pacific, which was good, but the means involved the slaughter of thousands of innocent civilians, which was bad. An even more recent example is the invasion of Iraq: it resulted in the removal of a dictator (which was arguably good) but it plunged the nation into civil war, again costing the lives of many thousands of innocents.
Lance's alleged actions pale in comparison, of course. I guess you should ask yourself a question: if want to achieve greatness, are you prepared to do just about anything to achieve it, including lying, cheating, intimidating, coercing, breaking the law, etc. Is that worth it? If success means misrepresenting yourself to the world, are you OK with that? Is it OK to be inconsistent and reward people for being dishonest? What does that mean for the integrity of a society?
If you believe in authenticity, if you believe in honesty and integrity, I don't think it's worth it. As for the supposed good Lance has done, Lance isn't a doctor and he isn't Jesus: he hasn't saved anyone.
He's been a really fast bike rider and made a stack of money. Maybe that's the real reason why people believe he deserves a free pass. Success equals virtue in our corrupted worldview. Don't fall for it.