Well, that is such a ridiculous thing to say, that I don't know where to begin. I suppose I should just say, don't make malicious accusations unless you actually know the person you are talking about. And their culture, for that matter.
Come to Japan, spend some time here, in fact, spend some time with Kawauchi. Doping by runners is just not part of the culture - it's not part of their mindset, they don't know much (anything) about it, and even if they did, would never consider doing it. Especially Kawauchi, who is just a young, naive, innocent, decent, hard-working guy. Don't scoff - it's true.
You shouldn't layer your own biases/experiences on top of people/cultures you know nothing about. I'm sorry, but you're just way off base here. I know you want to stick to your own beliefs (people believe what they want to believe) and attitudes, but you're going to have to trust me on this one. If you don't trust me, as I said, come to Japan and absorb the running culture. Just as very few Japanese cross the street when the pedestrian light is red, EVEN IF there are no cars in sight, no Japanese runners would consider taking drugs, even if they knew anything about them, which they don't.
"Gaman" - perseverance - is the Japanese runners' ideal - this is literally what they live by - they live to sacrifice themselves to their running - by running, not by cheating. It's true, believe me, it's true.