Cycling is one of the world's dirtiest sports for blood doping. One would be completely justified to assume that winning 7 Tour de France titles against a heavily doped up field would require some form of artificial (and likely illegal) performance enhancer. If everyone else is cheating, then the odds of that level of success done legally becomes more improbable, if not impossible. That being said, you can't impose guilt on an athlete until he tests positive (Barry Bonds notwithstanding), however likely you think it is that he cheated. Suspicion and indirect circumstantial evidence is not sufficient to prove guilt in our society (unless it is Barry Bonds).
Do I think Lance Armstrong cheated? Probably. Do I care if he did? Not at all, not in that sport. If they take a title away from Lance and give it to the 2nd place finisher, I'm willing to wager that guy probably also received an artificial boost. Add to that the fact that Lance is a cancer survivor and an inspiration to everyone with that malady, he's not someone I'd like to see publicly shamed after retirement (unlike Barry Bonds, whom I very much enjoyed watching his shaming). This crusade by the US federal authorities to strip Lance Armstrong of his yellow jerseys is ridiculous, and a precious waste of tax payers money. They spent millions of dollars on this investigation, money that could have been spent on advancements in drug testing.
Does the fact that everyone else was cheating make it okay if Lance did? No and yes. I choose to have my cake and eat it too. Cheating is bad and should be discouraged, but look forwards rather backwards, especially with the cancer survivor. Accuse me of selective hypocrisy if necessary, but I choose to like Lance Armstrong and disapprove of his punishment by his own government.