The scary thing is had Armstrong not tried to come back to cycling the last time he would've been in the clear. The reason Landis turned him in was Armstrong refused to let him on his team.
Which reminds me: Mr. Landis still owes me $35 for that book of his that I bought. [0] His book did highlight what an unprofessional ass Dick Pound (head of WADA at the time) is, and how loosy-goosy some of the testing was. But in the end, Floyd doped just like the rest of them and deserved to be stripped of his TdF title. Once Landis' story broke, I can say that's the point at which I just gave up on pro cycling. That's when it all became clear that cheating also includes lots of lying, and regrets only come when they're caught. I gave the whole lot the benefit of the doubt, and now feel foolish for doing so. I'm a former Cat 2 racer, USAC race official, paid loads of money for pay-per-view races, loads of money on gear; now I don't do any of it, and if I watch sports on TV it's MotoGP. Sports participation is now trail running, where the most insidious drug I see evidence of is the cloud of pot smoke rolling out of some dude's car right before the start.
If Armstrong had just left well enough alone, as you mention, he would have walked away a hero. But I'm guessing his cockiness caught up with him, and he just didn't know when to leave well enough alone, convinced that if he hadn't been caught before he'd continue to not get caught. Which seems to be the downfall of many criminals that get caught.
And as unprofessional as Dick Pound's behavior might have been, it turns out he was right. That's where I'm conflicted. Not "innocent until proven guilty", but "I'm convinced you're guilty, and whether you're guilty or not I'm going to dig until I find dirt". But he was right, at least this time.