The conclusion may sound redundant at this point, but it is fairly simple: if you want to have a discussion about Android and iOS (and there are plenty of incredibly interesting discussions to be had), think about the issues you want to cover, and break each down on their own terms. Trying to bundle arguments under and umbrella term like "fragmentation" is just lazy and it holds very little meaning at this point.
At the end of the day, I always get the feeling that the people yelling the loudest about "fragmentation" are people on the sidelines, who've never coded for Android at all. That's not to say it's not a problem at all - it's just to say that it's an area where the competition does a better job. Android's device diversity certainly creates additional challenges for Android developers, much in the same way that Apple's inconsistent App Store policies creates additional challenges for iOS developers.
Each platform has its weaknesses, but none have been as aggressively made larger than it really seems to be than Android's supposed fragmentation. Unravelling this positive feedback loop among these bloggers should make for fascinating material.