Almost literal Devil's Advocate mode: at the time, live-streaming Starcraft 2 was literally Destiny's job (call it cringe w/e but people were paying him.) Imagine some random asshole starts a long-term sabotage campaign against you working your job, and there's zero legal way to deal with the situation because the asshole lives in a jurisdiction where under aged people have almost zero criminal liability (until they turn 18, at least.)
Out of forced necessity, Destiny had to become the leading expert on how to protect a Twitch stream from DDoS (big part of this was, at the time, Twitch did not have their own systems in place to prevent/mitigate this issue. Or they were highly inadequate.) He arguably had exhausted every other legal measure to solve the issue, when he made that threat.
He still most likely shouldn't have done it, but I think this is important context.