To speak plainly, Lance never had to face the choice of doping to win against a field of innocents. Never. He had to face the choice of doping to level the playing field. He had to choose to leave behind a primary moral reality (do not cheat) and enter a world governed by a secondary moral reality (we are all cheating, so it’s okay if you do, too). So he did. In a world where there are only cheaters, there is only one morality that matters: “shut up and keep lying.” And keep snoopers from the primary world out of your secondary world. He and many others did that for a long time. He was tested endlessly and never caught. And he won.
I'm ambivalent and uncertain about the issue of drugs in sports. I think the ones we know to be dangerous should be banned for the athlete's own good. I like the talent of athletes competing on talent alone, but is a drug that enhances performance really cheating? Hmm... If everyone's doing it and everyone has access to it, maybe not.