Clean Eating vs IIFYM (What does clean mean?)

I have been training clients since 2008. Since then I have moved from Bro Science of Lean protein (Chicken& egg whites) Complex carbs (Oatmeal, brown rice, sweet potatoes, and healthy fats (olive oil & almonds).

Over my years of competing, studying and learning from others I adopted a more Bro/Scientific approach that Lyle McDonald call "Flexible Dieting". Many of the foods I eat and maintain my weight on today would never be considered when discussing losing weight but as If It Fits Your Macros (IIFYM) takes off so does the normal belief in traditional dieting.

I would like you to share your thought and help our community, (the chocolate thunder army) understand what we believe
1. clean eating is?
2. Is clean eating realistic and sustainable for the masses seeking to lose weight
3. How do you feel about IIFYM
4. Is there a limit to IIFYM? What is it?

As for clean eating means eating the most nutrient rich foods with the least about of calories. (Nutshell: you can eat a lot of it and not get fat)