I'm not sure what you're trying to say. That because doping happens at US Masters level, it surely must happen at higher levels? If so, what do you think about the possibility that it might happen there because it's easier to get away with it? Or maybe you were trying to say something different.
Also, if your friend quit because needles came out, I assume that means he's clean, so wouldn't his 'extensive international palmares' counter your assertion that we can't believe clean riders can do well?
Not pretending to know any inside info about the pro peloton, but I think it's too easy to be dismissive and cyncial (pro cycling has given us a LOT of reasons to be exactly that) without looking at other possible explanations.