I think that Mazal is correct. Diabetes is a serious illness. Like lupus, severe food allergies, psychiatric illness, or deafness, it can be controlled or compensated for.
If you want people to date people with diabetes, you have to acknowledge that it is a serious issue that affects every day functioning in an all-encompassing way.
I would be more worried about my child dating someone with diabetes who had the attitude “It’s not a big deal, I more or less have it controlled, don’t worry about future issues.”
I would be less worried about my child dating someone with diabetes who said, “Look, I know diabetes is a serious disease. I live a life of self-discipline and have it well-controlled for many years. I hope this will minimize the long term effects and I check with a doctor every time I notice something minor. The rest is in Hashem’s hands.”