The whole seed oil thing isnt that much of a conspiracy as it is completely blown out of proportion.

The core of it boils down to: An imbalance between Omega-3 and Omega-6 fatty acids causes and/or worsens inflammatory conditions. Seed oils (sunflower, canola, peanut, soy bean), especially the highly refined varieties, typically contain was more O-6 than O-3 fatty acids. So, if you stop your brain there "seed oils bad, use olive, avocado or (as our chronically online right wing twitter users probably prefer) non vegetarian or vegan fats like butter or tallow".

This however ignores and oversimplifies things massively. First of all, the balance between fatty acids is just one factor for inflammations. Secondly, hardly anybody consumes only one type of oil exclusively and especially not necessarily in the relevant amounts. Fried your mushrooms in canola and added them to a salad dressed in olive oil? Shouldnt be a problem.

The real issue that doctors warned against was the amount of (seed) oils hidden in already highly processed foods - every type of fat is replaced by a cheap, neutral tasting oil, most often canola, sunflower or soy bean oil.