Really? Explanation is not justification. It is unfortunate that said person was changed into a violent killer due to a brain tumor, but they are still responsible for their actions. How they are to be held responsible is not something that I’m defining in this case, and perhaps more challenging to identify, but they are responsible nonetheless.
How you conduct yourself is a choice. In a moment, you may react in a way that you don’t have control of, but life is made up of not a single moment, but many. What you choose to do with those subsequent moments is up to you.
Still, you are using an extremely narrow circumstance to justify, and excuse, a wider behaviour. Do people sometimes do things they regret out of anger, spite, or other reasons? Sure. Are those cases difficult to process and identify effective solutions to? Absolutely. Is this what leads people in WoW BGs to hurl insults at one another or to give up on a BG and not play, to the detriment of the rest of their team? Unlikely.
These behaviours persist because they are allowed to. Folks treat each other like dirt in this game and there are no consequences, so there’s no reason to change. Sure, there’s probably a person or two out there who just can’t help themselves, but again, those aren’t the folks we’re talking about. Trolling, insults, and nonparticipation are par for the course in BGs, not an exception. We see the same behaviours here, on the forums. People treat each other like garbage here. Discussions like the one we’re having right now are rare.
Consider FF14. They take a much more strict stance on such behaviours and, as a result, people treat each other much, much better in that game. You probably think to yourself, “Nah, it’s not like that.” Yea, it is… I didn’t think so either, but yep, it’s a much more noticeable, and pleasant, experience.
I’m not going to sit here and tell you that I’m perfect. That I’ll never make a mistake, get angry, or do something I regret. I’m human, after all, and while most of us have the free will, support, and tools to make better choices, our individual make up makes that difficult sometimes. But even where I to do that, I know that I am responsible for what happens and accept the consequences of my actions. I know I have a responsibility to make right what I did wrong, and have worked to do exactly that on those occasions where I have made those mistakes.
These are the expectations placed upon us as members of a society. They are ones that are reasonable to achieve for most of us. For those few who absolutely can’t, it’s up to us to find appropriate was to handle it, but for those who simply won’t… they need to be held accountable for their actions.