If you're not talking about blood sugar spikes I'd say there's even more of a reason for people to eat fruit as fruit is extremely low in fat (aside from avocados, etc) because lower fat means better insulin levels (type 2) in general as insulin resistance is almost entirely determined by fat in the bloodstream blocking glucose from entering cells.
Juice, yeah, that's horrible for diabetics, even if you're doing lots of exercise it's just a disaster.
https://www.ncbi.nlm.nih.gov/pubmed/15650564
Those who wish to follow a low-carbohydrate diet should be encouraged to follow a new menu low in fat, and with most of the protein derived from plant sources.
If not fruit what could a diabetic possibly eat in it's place? There's no better carb in general other than potentially sweet potatoes, and it's unadvisible to have any more fat than absolutely necessary, and lean protein is rare to find unless it's in plant-sources as well is generally not beneficial to ones overall health in excess. Furthermore protein also requires insulin to metabolize, thus increasing insulin needed and thus insulin resistance.
I would disagree with some of your discussion on protein. While insulin is involved in protein metabolism, it does not elevate blood sugar. If you give a Type I diabetic a steak with no short-acting insulin, you will not see much increase in their blood sugar.
Furthermore, you talk about resistance. Resistance has everything to do with fat...as in excess weight in an individual...however, if a skinny individual eats fat it is not like that specific fat is floating around the bloodstream causing insulin resistance.
High fat foods should be discouraged because of its potential for weight gain. Sugar will eventually lead to more fat storage as well.
https://www.ncbi.nlm.nih.gov/pubmed/9416027
My recommendations: Eat the meals that are lower in carbs and eat protein that is lower in fat. If you do this, you will decrease your overall calories, lose weight, and have less insulin resistance.