>How should using processes not used at home make something harmful?

Well, for starters - the refined sugars, carbohydrates and oils that seem to be the main culprits behind the obesity epidemic are mostly things that wouldn't be efficient (or in some cases, even possible) to create in a home cooking environment.

Sure, you could order some grain milling or oil extraction equipment on Alibaba and DIY it, but 99.999% of households aren't going to do that.