It is my understanding that the Swank diet is low carb, as is the Eskimo diet according to GaryTaubes in his book Good Calories Bad Calories (MS is virtually nonexistent among the Eskimos; among Lapplanders, too.).
Any carbs are complex carbohydrates for the most part, and do not trigger spikes of insulin secretion.
When the pancreas secretes insulin in response to glucose in the bloodstream or in response to the ingestion of simple carbs, which convert quickly to glucose, the pancreas secretes a generous amount of insulin -- more than adequate to handle the glucose amount. It is this excess amount in the bloodstream that I believe causes blood vessel damage and initiates the immune system action.
I don't believe the amount of fat in the diet, whether saturated or otherwise, plays any part in the insulin hypothesis -- it is basically neutral. A fatty diet may even prevent insulin from being absorbed in the intestines; if so, a fatty diet may actually help MS.
But remember, these wild ideas are just mine -- I have found no experts who agree with me yet. Only my husband and a few friends think these ideas are possible.