The Okinawans got their carbohydrates primarily from vegetables with a low glycemic index, primarily the imo sweet potato (http://www.huffingtonpost.com/dan-buettner/okinawa-blue-zone...). They also consumed a decent amount of Omega-3 fatty acides, since they ate fish three times a week; fish that was likely not contaminated with mercury or factory farmed. It's worth noting that once sugar and refined carbohydrates were introduced into their diet, they went from having the highest longevity out of 47 prefectures in Japan to the 26th (http://www.telegraph.co.uk/news/health/news/3342882/Japanese...). That article came out 10 years ago, and the situation is worse now (haven't been able to find any written sources for this, but it's explained in the documentary 'Sugar Coated').

As a counter to the Okinawans, we can look at the Maasai people of northern Africa https://en.wikipedia.org/wiki/Maasai_people#Diet, who exclusively ate meat, milk and blood from cattle yet had no incidence of heart disease, cancer, tooth decay, or obesity.

I think the point here is that we haven't really honed in on what exact macronutrient composition is the perfect one for a human body. Humans appear to adapt well to any macronutrient composition, as shown above by the diets of different cultures (I think if you took a global survey in 1900 of what different societies were eating, you would find all manner of different diets but very low rates of disease in all or most of them). What we have identified is that we're seeing unprecedented levels of cancer, obesity, alzheimers and cardiovascular disease. So the question to ask is "What changed in the past 50 years?" I would say it's a few things (ordered by severity):

1. Sugar. We don't need sugar to survive, yet we eat mountains of it.

2. Refined, high GI carbohydrates.

3. Vegetable oils. Seed oils like canola, sunflower, or palm oil (not Olive/Avocado/Coconut oil) are high in pro-inflammatory Omega-6 fatty acids and polyunsaturated fats.

4. Factory farmed meats, also high in Omega-6 fatty acids.

You can find counterexamples to any macronutrient focused diet, as we did above, but there doesn't exist a society that consumes sugar, refined carbohydrates, or vegetable oils in abundance and still lives long, disease free lives. To date, there is no counterexample that says the modern western diet is in any way healthy.

Regarding the studies you mention, I don't doubt that heavily processed meats like bacon and sausages are bad for you, though it's because of the Omega-6 fatty acids in factory farmed meats which are known cause arterial inflammation and contribute to atherosclerosis (grass fed beef, pork, or pastured chicken does not have this problem). That said, I am heavily skeptical of any studies that show 'links' to cancer. Just because two things correlate doesn't mean that one causes the other. Nutritional studies are notoriously difficult to conduct accurately, and have been plagued with bad logic (correlation != causation), bad statistics, and perverse incentives (such as the incentive to reach an interesting conclusion or risk losing government funding) or conflicts of interest (being funded by the sugar industry or big pharma). You ask for a good source (not blogposts/youtube videos) on what the OP posted; in kind, could you link to the studies that you're talking about?