What's Wrong with Hydrogenation?
Unlike butter or virgin coconut oil, hydrogenated oils contain high levels of trans fats. A trans fat is an otherwise normal fatty acid that has been "transmogrified", by high-heat processing of a free oil. The fatty acids can be double-linked, cross-linked, bond-shifted, twisted, or messed up in a variety of other ways.
The problem with trans fats is that while the "business end" (the chemically active part) is messed up, the "anchor end" (the part that is attached to the cell wall) is unchanged. So they take up their position in the cell wall, like a guard on the fortress wall. But like a bad guard, they don't do their job! They let foreign invaders pass unchallenged, and they stop supplies at the gates instead of letting them in.
In short, trans fats are poisons, just like arsenic or cyanide. They interfere with the metabolic processes of life by taking the place of a natural substance that performs a critical function. And that is the definition of a poison. Your body has no defense against them, because they never even existed in our two billion years of evolution -- so we've never had the need or the opportunity to evolve a defense against them.