A few general points:
- I can't speak for everyone, but it doesn't have to be a matter of "Kenyans are dirty, but Americans are clean". Every nation cheats to one degree or another. I would assume people of any nationality have a tendency to cheat if the rewards are tempting enough, the drugs are available, and somebody has the know-how to administer them without being detected.
- One can accept that Kenyans are in general better runners, AND that they cheat. I have no problem with the claim that on a level playing field, Kenya/Ethiopia/Somalia etc will produce more elite runners than the USA/Britain/Germany etc. I just don't think that means they don't also cheat. Just like the US produces way more quality 400m runners than any other nation, but still, some of them cheat.
- It would be hard to argue with the claim that a rapid drop in almost all the distance world records coincided with the spread of EPO in sports. It's well-established from cycling history that EPO became prevalent fairly suddenly in the early 90s. That was also when track's distance records were lowered by large margins. Now, you can argue that this was just a coincidence, but you can't deny the timing.
- Given the fact that cheating DEFINITELY DOES take place in Kenya (by which I mean, at least some elite runners from Kenya have tested positive); and given the fact that EPO seems to be rather easily available (by which I mean, when I get the flu, I don't think there is a doctor or pharmacist in the whole US who would propose injecting me with EPO, but apparently this can happen in Kenya); and finally given the fact that Kenyans over the last several years have suddenly produced literally dozens of marathoners running under the world record of only a decade or two ago, mostly managed by Europeans who presumably aren't doing it as philanthropical work - you can at least understand that some people might be a little suspicious.