Link between impotence and diabetes?

Why would diabetes cause impotence?

Diabetes and erectile dysfunction are related by cardiovascular damage

Erectile dysfunction is very common in men with diabetes. Erectile problems are especially common in diabetics who are also obese. The risk of developing erectile problems is three times more likely in diabetes than non-diabetics. Because of the strong link, men with ED should be screened for diabetes. Patients with diabetes and ED have an increased risk of undetected heart disease.

There is a high proportion of men with insulin resistance who also have ED. Insulin resistance can cause damage to cardiovascular system, including the blood vessels that flow to the penis.