Spontaneous bruising can be caused by leukemia. He needs to find a doctor who will take this seriously!
Did the dr. run any tests? It doesn't sound normal to me to have bruising all over from diabetes. I would keep a close eye on this and if you don't feel you are getting the answers you want then call them back. Ask why the bruising and have it explained. Ask if they can do blood test to make sure spleen and liver are okay and blood counts and clotting factors are ok. Remember: they work for you.
He should see an Endocrinologist, a doctor who specializes in diabetes care and treatment. His lifestyle and medication has to be closely scrutinized and changed if need be. Do not depend on an ordinary doctor for further care.
This is what I found on the iNet; There are two occasions when bruises might appear if diabetes is the source. The first condition is named acanthosis nigricans. With this condition, our skin might exhibit black or brown discoloration in the folds or creases of our body. This is usually a situation something that occurs on the neck and inside the armpits. This happens because insulin has suffused in the skin, and it is often considered to be a symptom of Type II diabetes.
The other condition that may affect you is the fact that normal healing times can be diminished in people who have diabetes. HTH. Good luck.