Please compare hydrogenated lard or tallow to hydrogenated corn oil or olive oil, et al, ETC. Thanks?

I have been reading various sites that make a good case that saturated fats are really ok, and it checks with my gut feeling. I was raised to think they were evil and grew up eating tons of soybean oil in every form known to mankind. I am now scrambling to salvage my health. As I now understand, naturally occurring fats, whether saturated, such as coconut, tallow, or lard (is chicken fat saturated?) or unsaturated (or is it mono something?) such as cold pressed olive or sesame oil are ok, but not the chemically extracted oils such as cottonseed or corn oil. Or are they extracted by high heat, or both? Anyway, what I REALLY want to know is what hydrogenation does to any or all of these? Any other knowledge pertaining to fat is also welcome!
I mean both. I want to know in what way hydrogenation changes these fats and I also want to know why these changes make hydrogenation bad for people. As I understand it, whether saturated or unsaturated is good, any kind of hydrogenated fat is bad, right? Why?
And if saturated is bad for us, why, and if chemically made oils are bad for us, also why. Partial answers to any of this helps. Thanks everyone!