First, as a practical matter I don't see any scenario in which Rondo is not made captain - outside of him getting traded. There's no other realistic candidate.
Beyond that I also don't see why there would be any fuss about such a move.
Go back and read about Larry Bird, or Michael Jordan, or Kobe Bryant. Those guys all went toe-to-toe with teammates, coaches, refs, other players and anyone else on numerous occasions.
I'm not saying that such a leadership style is the best one in terms of getting the guys around you to play better. I actually think it isn't. But, painting Rondo as unworthy of being a captain seems extreme given that what he's done is not too different from what many other team leaders have done in the past.