[WS:] I think there is more into his argument than that. As I read it, he argues that US labor movement have not transformed into a political force representing the entire working class, as many of their European counterparts did. Instead, the movement never transcend trade unionism model of operation - delivery of work related benefits (higher wages, insurance etc.) to members only. The fragmentation, the patronage, the fiefdom structures and corruption were just the consequences of that initial strategic choice. Your argument seem to miss that, which is like missing a forest among woods.
I have to agree that Fitch's book could be better written, he goes on tangents quite a bit, especially when he talks about corruption. I do not think that his writing makes a compelling argument linking particularistic "business model" and focus on benefit delivery over political representation of the entire working class with the consequences of that approach - fragmentation, fiefdom, patronage, corruption and eventually loss of popular appeal. But I think the connection is there, and you need to read his book as if you were eaten a crab - do quite a bit of work of digging though the shell and gills to get to the choice morsels of crabmeat inside.
And that he get a fact or two wrong every now and then? As Nietzsche said, errors of great men are venerable because they are more fruitful than the truths of little men. In my view, Fitch said something very important about the US labor movement which is worth repeating and amplifying. So what that he got a few details wrong?
Wojtek