Dr. McD tried to facilitate that by having Fuhrman at the last Advanced Study Weekend. Fuhrman then went home and since then has redoubled his attack on rice and taters. But Dr. McD did try!
Why? If he sees all the success McDougallers have had for decades, eating grains and starches - with many reversing their diabetes - what possible foundation does he have to suggest that whole grains should be avoided?
There are many individual choices to be made regarding each diet, or combining each diet. Some people may choose to eat more nuts, or more fruit, and others find they can eat more whole grain bread. But that's different than completely villifying the foundations of any particular plant-based diet, which is what he's attempting to do to McDougall's.
Fuhrman's diet is a lot more fruit based than McDougalls, but obviously, this works for many people. So, McDougall isn't saying, "Fruit is bad. Avoid it!". He doesn't seem to believe fruit is an optimal weight loss food, and perhaps Fuhrman feels the same about the potato. That's fine - let people decide which diet works best for them.
But don't suggest that rice or potatoes cause diabetes. He knows better than that. If he doesn't, I'd question his credentials. Does he believe Barnard, Esselstyn, and T. Colin Cambell are misguided too?
The potato, particularly, is one of the best tools we have for encouraging people to explore the plant-based side. Low carbers are all starving for potatoes! If you tell people you're vegan, they just imagine a diet of greens and fruit smoothies, which doesn't get their appetite watering, but if you tell them you're eating all the potatoes you want, their ears perk up.
So, I think there better be very compelling and scientifically proven reasons to start limiting the plant-based menu. It's already an uphill battle to get people to change to this way of eating, so why would anybody on the plant-based side attempt to restrict variety?