A. Less than 0.5% of the population is hardly a "hold" on the human race.
B. If milk were really the reason for Type 1 diabetes, those identical twins fed similarly as babies and young children would see a higher onset of T1 in both twins. This isn't what happens, so milk cannot be the key factor in this onset. The same reason why genes aren't the whole story is the reason that milk isn't.
I believe there's a cascade of environmental events that trigger Type 1, so no simple answer sadly.
However, studies have shown that being breastfed reduces the chance of Type 1 (and Type 2 too) as well as its many other health benefits. So certain milk is good