Kurt Harris had a rant about the processed = bad idea that I'm not finding now so I'm going to have to paraphrase.
Processing, in and of itself, is not a bad thing. It's how we get cream from milk, butter from cream, yogurt or kefir from milk, etc. Fermented vegetables? Processed. Dry-aged meat? Processed. Rendered tallow/lard? Processed.
What you need to consider is what is added, what is taken away, and what is changed. When you process corn to get corn oil you are concentrating the oil, something that corn does not have a lot of in the first place. Now you have an evolutionarily novel amount of something we can safely consume.... in small amounts. When you cook a tuber or vegetable the plant's cell walls burst, releasing the starches, sugars, and other nutrients. We need fire for this because cellulose is indigestible to humans.
The problem with grains is not the amount of processing that's necessary to make them edible, it's that they are more toxic than most other edible plants. By the way, cassava, one of the "safe starches", can induce cyanide toxicity if not properly prepared. But if you follow what needs to be done, it becomes safe and non-toxic to consume. Gluten proteins are very difficult to digest, and I don't know how much of this is fixed by following traditional preparation methods (sourdough fermenting). Non-gluten grains are easier -- brown rice can simply be polished to be in the clear, others might need some soaking, sprouting, or fermenting.