I don't know about that. in my view, you can call him a murderer, genocidal, sociopath, anything related to his actions. But calling him an epithet, comparing him to an animal is a different thing. Even physical violence is more tolerable. of course people can say whatever they want in private, i'm talking about public discourse. terms like "monkey" and "dog" have been used across cultures to mean really nasty things. It's dehumanizing (literally!), it says as much about the speaker as it does about the subject.
> comparing him to an animal
homo sapiens is an animal species.
when humans say "an animal" in the English language, they're referring to "non-human animals". Being called an animal in itself isn't insulting either before you go there. Hardly anyone would be insulted at being called a lion. I think everyone who can read understands exactly the implication being drawn and the dehumanizing being done. Everyone from slave traders, colonialists, nazis,etc.. have used "monkey" to dehumanize people. Same with "dog" , "snake" ,etc.. in different contexts.
Tomatoes belong in fruit salad, and the cause of every plane crash is gravity.