First off, I want to clarify that I called your argument in the post preceding that pathetic, not you, so I apologize if it came across as that. I was drinking while replying that time. Calling people names helps no one.
Do you really not see the difference here? Luffy sees Zoro killing people who threw them a party that night, and he attacks him to stop him, and eventually the misunderstanding is resolved. Garfiel knocks out, imprisons (gagged and tied up like a pig with no chance to explain himself), and eventually kills Subaru (or at least directly drove him to death via rabbit) for smelling like something and openly admitting to being able to do something he shouldn't be able to (versus not saying anything, the better option if you are plotting something). Just to be clear, Subaru would've died in Garfiel's hands if he hadn't escaped the barrier and got rabbited, so arguing the technicalities of that is pointless.
Don't move the goalposts. My assertion from the very start that Garfiel was evil for everything he did, not just the knocking out and imprisonment (although that is already bad in itself). You said those were non-violent methods, which is ridiculous on your part, and defended it by saying anime does it all the time. But it really doesn't. You just decided to stretch out the meaning of "on assumption" to cover any misunderstanding. So to clarify what I meant when I said that, it is being punished on assumption when he has done absolutely nothing wrong. This has always been the underlying premise of everything I said, which you can easily see if you re-read my posts.
Would I call Garfiel a monster (your word, not mine, btw) if he decided to talk it out with Subaru when he was trying to escape the village? Maybe not. I would think him a stupid, brash asshole who deserves a beating and imprisonment.
But he not only decided to forgo discussion, he murdered Otto, maybe Ram, a bunch of innocent villagers, and essentially Subaru, for no wrongdoing or reason really. That's why he is evil and should die. Some things you can't excuse by saying "he was out of control," assuming that was even the case. He could've just, I dunno, stopped fighting before going berserk? Are we going to say drunk drivers are no longer responsible for killing people because they were out of control?
To bring up another point, why would Garfiel's actions be less deplorable if it were commonplace in anime anyway? Shouldn't we just see all these actions as evil regardless? If we use commonality of an action as the basis of acceptance, then there is no longer any moral argument to be made.
That said, I still definitely think that Garfiel's actions are evil even when seen through anime moral standards. Those are the actions of a villain. Anime heroes (the characters with supposedly the moral high ground) don't do all the things he did.