Saying that you'll kill someone is not proper figure of speech, so please don't give me crap about it. It is not a proper figure of speech as you're still expression violent over the other people. Which is why, if you say that in public you can be arrested/charge for verbal threats.
I got in trouble at school because, I jokily told a friend that I will kill them. I got in trouble because of the improper usage of it.
I was correct in my statement that regardless that you seriously meant it or not, is not showing that you're peaceful and you're just making yourself look more silly.