The problem is not in dairy's "bloat" itself, or that it is not a viable source of protein. The problem is that over half the population can't properly digest it, and because of that, it can be abruptive to the absorption of a variety of other minerals and vitamins, in particularly zinc. Improper digestions and gastorintestinal distress can also lead to a rise in cortisol, which in turns lower FGF2 in the brain, potentially resulting in anxiety and depression in the consumer (that's a simplifed version of one of many pathways improper digestion affects neurochemistry). Also, improper digestion can undoubtedly impede performance. After the agricultural evolution, although the AVERAGE lifespan increased as infant mortality and starvation decreased, the health of the average person also took a toll as we relied on a variety of foods that are less nutrient dense and we can't digest as well. Lactose is a tricky saccharide for the human digestive system and choosing not to drink milk, for those I know of, is a conscious, educated decision based on the way it affects performance, the potential detriments to health, and the negative impact it could potentially have on longevity. Am I saying that milk products should be avoided by everyone, absolutely not. They are an affordable, calorie-dense food that can undoubtedly help those who are not so lactose-sensitive to grow. I myself keep some Greek yogurt around to use instead of sour cream in some instances, or if I'm in a rush at breakfast. \The natural cultures in the yogurt usually don't upset my stomach as much as cheese or milk. The point is, the reasons to avoid milk go far beyond the bloat, and if you've never tried training after being completely off dairy for a month, I suggest you at least try it. You may not know how good you actually feel.