"If Lagat was still a Kenyan, do you think he'd have had a slow start this Summer? Smoke that in your hypothetical pipe."
I have absolutely no idea. Maybe? Does it matter?
The point is that it is objectively harder to make a Kenyan world team at 1500m because 1) the talent pool is deeper, and 2) the Kenyan federation injects a significant element of subjectivity into the selection process.
Assuming that Lagat would have had the same slow start in Kenya as in the US, emigrating from Kenya makes sense. I have no idea whether this is a fair assumption, but the point stands: it's easier to make the team as an American.
Why are people getting so riled up about this? I think it's a pretty straightforward argument, and one that can surely be conducted with a reasonable standard of civility.