It’s a joke, see. Because if you murder someone, you can get off by pleading self-defense. Joke.
I just read a bunch of notes that seemed to take this line very seriously – that Ophelia drowned herself in defense of seeing more death and destruction. I mean – come on. Joke, man. It’s a JOKE. The character making the joke may not realize that it’s a joke but it’s a joke nonetheless. It may not be a particularly funny joke. But joke.