Thank you for contacting us. No one wants to have the extra challenge of having to deal with a medical issue, and the attention to detail and restrictions that go with it. Your son is probably angry about having to tend to it, but as you know, his life and/or quality of life depends upon his attention to treating it.
We do not know if the anger and aggression you are referring to is specifically geared toward the diabetes. Or, if the direction and instruction you are giving him regarding it, is a separate issue. If it is related, validate his feelings. He has a right to be angry, but how he deals with that anger is what counts.
How old is your son. The younger children are, the less choice they have in certain matters. You can let him know he does not have a choice in the matter just like he does not have a choice in whether he has to wear a coat in 10 degree weather. Treat the diabetes, and continue to teach him how to treat it and take care of himself so he can lead a long, healthy and productive life.
Yes, it is hard to monitor when you are not there, but talk to his physician about any and all options to simplify his treatment. Stock your home with foods that are healthy choices for him and gear away from all other food options. Have him work with a nutritionist (perhaps that will appeal to him more than the word "counselor.") He may not want to feel like others are controlling him, but with some of this, he may be empowered to take control himself.
There is even a camp in Nebraska for children ages 9-18 with diabetes. A friend's daughter attended for years and then even was able to come back as a camp counselor when older. It is called Camp Floyd Rogers. You may reach them at 402-885-9022, if you think this might be a good option.
If his aggression goes beyond this, consider calling in for more strategies, and sharing what you have already tried.