There is one problem with the "They were all doping" argument. Many of the athletes that were doping only did it because it was the only way to compete against the dopers. If a coach tells you that you're never going to have any success unless you dope and all you've ever wanted to do was be a pro cyclist, it makes for a very difficult choice. Certainly every one that makes that choice has to face the consequences, but I can understand the pressure they felt.
I have no idea how long the doping was going on or who started it, but the early dopers are the ones that really f'd things up.