I mean, now that I think about it, a lot of great defensive or great coaches that have won championships have had a good PG.
Doc Rivers = Rondo
Larry Brown = Billups
Greg Pop = Parker
Phil Jackson = Fisher
Those have been the four teams to win it all form 2000 to 2010. Fisher is the weakest out of all of them, but in his prime, he was a solid PG, and even today, he never turns the ball over and is super clutch. If anything, good PGs help command the floor, which can be very helpful to a defensive minded coach. I think it's a big reason why Tom Thibodeau is having great success with the Bulls. He's an amazing defensive coach, but it sure helps when Derrick Rose is commanding the offense.
LBJ is no Magic, and heck, while he is a good if not great passer, he's no Kidd, Rondo, Nash or CP3. He's not much of a floor general either like Tony Parker, Fisher, D-Williams and Billups. Wade is a scorer.
Edit: Why do I have a feeling both LA and Boston were looking past their matchups tonight for the Sunday showdown? Boston game got a bit ugly. KG elbowed Frye in the nuts, and there were 6 T's given out all at once.