Damage his reputation w/ which demographic/target-group/audience? Hardly making any pronouncement on LA's legal/criminal liability here, but it bears mentioning that not all of the public thinks like The Clinic and there will certainly be not insignificant segments of the population that really don't care about whatever cheating they may be compelled to realize Lance engaged in, if such an allegation were to be proven in US court. This is America, man, where Michael Vick - who served 21 months in federal prison + 2 months home confinement - is now QB for the Philadelphia Eagles. That's a pretty exalted position position for a sportsman, as there are...what, 30 teams in the NFL?
The people who already think LA are guilty are still going to think he's guilty. The question is whether or not they're going to care enough to treat Armstrong differently than they would a post-prison Michael Vick.
The Clinic is not representative of the way in which John Q. Public thinks about someone in Lance Armstrong's position. Call it unfortunate or not, but it's reality.
Cycling is such a small sport relative to the NFL (even smaller on the national level) and yet Armstrong is bigger than someone like Vick (w/ respect to current and future notoriety amongst the American public) - I just don't see there being a worse public reaction to him for having committed fraud or tax evasion or whatever (should any of that be proven) than the reaction to Vick for having led a dog-fighting ring.
[note: in comparing Armstrong to Vick, I fully realize that there is no empirical methodology used here to rate them. I just cited Vick as a somewhat similar case, to some degree.]
End of the day, even if proven in US court to have committed a crime, I don't see Armstrong suffering any worse than Vick (and he's certainly in a better position financially, and w/ respect to interconnected web of vested interests backing him who aren't prepared to abandon him wholesale and will maintain at least a qualified support). Time will tell.