To be fair most raging isn't that much of an issue, but you'd be surprised how much of internet "insulting people" that "should just be dealt w/ by having thicker skin" constitutes assault legally and could get you arrested if you were doing that in say a public place of business or something.
Perhaps the player was very specific in their threats, or very specific about threatening themselves bc they were upset about something and depressed. W/out context it's somewhat foolish to dismiss something that seems to be having more impact on this person than the average troll. It's particularly interesting that he's not saying the person should be banned, but rather might need help (seeking care for the person rather than anger asking for punishment is rather the opposite of what you're implying w/ this post).