Coffee and Caffeine FAQ

While you are right that high sugar levels (hyperglycemia) are dangerous in the long term, it should be noted that low sugar levels (hypoglycemia) are much more so and can be immediately lethal. Many diabetics have a long period of high blood sugar before they are diagnosed, with little more harm than the classical symptoms such as thirst, frequent need to urinate, bad breath etc. Severe problems take a long time to develop.
I've never heard that diabetics should be likened to people "who have had a heart attack already." Diabetes is a serious condition and needs to be treated, but that sounds overblown.