Linux is not "fragmented". It is adapted to multiple environments and capable of running the same tools and applications on the vast majority of them. Those environments where you can't run, say, Konqueror are probably not suited for desktop browsing in the first place.
To pick a random example, I could run abiword on my old n900, my desktop computer and, with a bit of tinkering, my router. Okay, a lot of tinkering, and it's probably not much fun running a word processor and all the other bits necessary to make that happen on a router, over a vnc session. It would be a dog.
But that's sort of the point. Linux doesn't fragment. You wouldn't want to have the exact same user experience across divergent devices. By the logic you're employing, Apple is fragmented because it has completely different user interfaces on iOS and OSX and can't run the same applications. It's a laughably stupid argument, yes? So why are you making the exact same laughably stupid argument about Linux?