Just say for a second he was clean. Most if not all of the top 10 were caught for steroids, EPO and other shit. If that was the case and Armstrong still beat them, that would make him a superhuman. The fact he could beat the top racers in the world who were also on drugs while being clean himself is just not possible.
He did say one thing. He never said he was clean, he just said that he played by the rules. So who knows what shit he was on, but because it was never tested for meant he wasn't breaking any rules.