Well steroids and doping are different because they effect your body but sure, if Armstrong had cheated during trials with something like a small motor but not during the actual tour it would have tarnished his legacy but I don't think it would have ruined it like his cheating did.
It sounds like he's saying he cheated to get to where he was going faster, but that he would have gotten there eventually so it's fine.
It would be like Armstrong saying he only cheated during trials and training.