Well of course they do, but not like vampire bats or Count Dracula. They are known to be somewhat ferocious, and make a lot of noise, which could lead to someone believing they are like the tasmanian devil. They feed on smaller animals and make a racket and a mess when killing them. But they aren't some sort of bloodthirsty freaks. Your jackass friend is somewhat correct because blood is part of any carnivore's intake. But fishers aren't bloodthirsty or do it for pleasure.