I never believed the whole Rondo is a cancer narrative but I suspect that what Doc described is pretty accurate. He didn't say "Rondo was a great leader" and he didn't say "Rondo was a cancer". I think he described that at times, it was "hard" with Rondo but that they were able to always get through it and in the end there is mutual respect.
I suspect that at times, it will be hard for Rick Carlisle too but I don't think Rondo will be either a leader on that team or a cancer. The problem with Rondo is that he can't shoot and that after missing shots, it gets in his head and it starts to affect his game. I think at times, he also tries too hard for triple doubles but I would not expect that to be a problem on Dallas.
I don't blame Ainge, I don't blame Rondo, I think it was just time for Rondo to move on. Like breaking up with a girl friend; it is hard even if you know it is the right thing.