Comparing things in isolation like that is not very useful because you need other nutrients too. If a person ate 1800 calories from milk, orange juice and some amount of white sugar, honey etc. I don't think they would be more likely to develop insulin insensitivity. Sugar shouldn't be eaten alone. I'm not sure if this is true, but Ray Peat here claims that potassium has a similar role to insulin, so eating fruits and milk won't negatively affect your blood sugar as much - https://www.youtube.com/watch?v=bYAihAkCaw8