Scrutinizing Guidelines: The BMJ questions the validity of current guidelines for the management of cholesterol in diabetics. The authors review all the current studies on cholesterol therapy and outcomes and find them wanting when it comes to applying them to diabetics. They conclude that our current practice is based more on opinion than evidence:

Current recommendations to manage dyslipidaemia in diabetic patients are based on observational evidence and expert judgment. The heart protection study showed that simvastatin significantly reduced the risk of major vascular events for diabetic patients without coronary heart disease at any initial low density lipoprotein concentration. It remains unclear whether the benefits of statins are mediated by lowering low density lipoprotein concentrations, whether goals of treatment should be expressed as low density lipoprotein concentrations, and whether a fixed dose of statin, increasing doses of statin, or multiple drugs can be used to achieve these goals with acceptable safety. Recommendations from policymakers and experts should reflect this uncertainty.

Yes, it should. Yet, the current recommendation to keep the LDL cholesterol to less than 100 in diabetics is often characterized as "practicing evidence-based medicine". It may be based on evidence, but it’s not good evidence.