In all fairness, not all doctors are against low carbing as a means to control diabetes. Mine was 100% in favor of my going low carb to control my blood sugars and has been very impressed with the results that I've gotten.
As for the "Old School" of thought, I guess it would depend on how old the school is that we are talking about it. My dad first started practicing medicine in the 1940's and tells me that low carb was the diet of choice (at least in the Netherlands) at that time for diabetics. Of course, they also prescribed a low fat version, but at least they had the low carb part of it right. He still doesn't understand why the recommendation was changed to allow diabetics more carbs and doesn't approve of it. He's been very encouraging to me with what I'm doing and we've had some interesting discussions about the high fat portion of the diet (which we don't agree on BTW), but my test numbers speak for themselves on that matter.
Slowly but surely, more and more doctors are starting to come around to the idea that the best way to control diabetes is to cut the carbs, I think in large part because more and more diabetics are getting fed up with uncontrolled blood sugars on the standard diet now prescribed and are taking matters into their own hands and they see how much better their patients are doing on it.
Since the ADA isn't likely to change their position on this anytime soon, it's up to US to tell our doctors what's working for us and educate them that way. I would hope that results speak much louder than official positions of organizations.