At the elite level it is all about being able to process oxygen. The difference between the front of the peloton and the rear is a very small level of processing of oxygen. And therefore, as I have understood this over the years, you really can't compete without the doping. The testing to detect the doping hasn't kept up with the masking technology.
I am not sure that matters. I am not inclined to defend Armstrong. However it is troubling.