A) Fat has never been shown to clog/destroy our arteries. Also arguing with the fact that humans can store and burn fat is sheer lunacy. This isn't a big confusing thing based on meta-analysing the foodstuffs of a remote mountain populace, it's an observed biological trait. Humans can use fat.
B) Herbivores technically eat the results of fermentation in their stomachs, which is mostly fat anyway.
C) No clue about the differences in body fat metabolism between carnivores and herbivores but on the surface they look pretty much the same.