In creating the character of Taz, Warner Brothers was building on precedent. The person who described the Tasmanian devil (Sarcophilus harrisi) for science, in 1807, surveyor/naturalist George Harris, told the world how ferocious, fiendish, savage -- “uncontrollably wild” -- devils were.
He wrote, “They bite frequently and snarl and bark loudly.”
But here's how he knew. He had two devils. He kept them in a barrel. Chained together. They are nocturnal, and slept all day, while Harris was writing insulting things about them. They woke up when it got dark and discovered they were still chained together in a barrel. They fought and shrieked all night, when Harris probably planned to sleep. Perhaps he felt that if he had been chained to another guy, in a barrel, he would have remained quiet and sweet.
Tasmanian devils still have a terrible reputation. People call them vicious and impossible to tame. But Grzimek's Animal Life Encyclopedia, where I first learned about Harris and his barrel, also mentions a person who had two pet devils whom he leashed and took for walks. And there was no trail of bloody bodies behind them, even when he took them to Melbourne.
Others say they are “delightful and affectionate pets.” When not chained in a barrel. It's easy to find video of devils scampering across verandahs, hanging from sleeves like Jack Russell terriers, or in one remarkable clip, nestling in a zookeeper's arms and being persuaded to relax her pouch to reveal two infant devils (imps?) clinging blindly to her nipples.
It's true that Tasmanian devils yell a lot, specializing in a noise that's partly screaming and partly retching. Carrying on at night is how they got called devils in the first place. They are not as timid as people like wild animals to be.
They hold an ecological niche—that of a small scavenging carnivore—that gets bad press even without the shrieking at night and George Harris slandering them. (Also: chicken-snatchers.) Essentially they are marsupial wolverines. And you know how people talk about wolverines (Gulo gulo). For some reason people enjoy the idea of a small demonic animal and promote the legend of its savagery.
I once met two hand-raised wolverines. The minute they saw you they rushed up scrabbling over each other to lick your hands (and see if you had been nice enough to bring snacks). Like puppies, they loved to be rubbed and scratched. I'd love to meet devils raised that way, with affection. And no barrel.