Every time I see one of those "Home owner shoots gun at intruder, kills loved one by mistake" memes or stories, I have two thoughts:
1) Well, shit, that's only going to get worse, and blah, blah, blah. You've seen my rants about irresponsible gun owners, so you know where I stand. The point is that I "blah, blah, blah" cut myself off, because there is no value in flogging the dead loved one. Seriously. That's just adding insult to inury.
2) This person will probably never forgive himself, or herself, especially if that person was gung-hu macho about taking ouut an intruder. This person needs a bit of compassion, and I'll give that by not spreading the story, and allowing the person to grieve in what peace she can get. These poor people made a horrible mistake - they don't need every asshole on the Internet sending them "way to go dumbfuck!" emails or letters.
Sometimes, the best way to make a point, is to just say nothing at all.