Without data it's hard to tell what is actually going on. I suspect that an algorithmic focused company like Google is aware of click-after (or whatever it's called) rates of videos on youtube.

It's certainly plausible that viewers of the linked video do enjoy watching shocking deaths on camera (for the record, I have a G+ account and am logged into youtube and also see the same video as the 3rd related video).

Without persistent tracking information I'm not sure how you could make this better. On aggregate, people who watch a music video by the Dead Skeletons tend to enjoy also watching shocking deaths on camera.

My guess at a solution is for Google to do more tracking. They obviously don't understand that you don't watch or appreciate watching people die, so why show it?

Edit: If, while you're logged in, you could "X" out videos you don't watch in the suggested video list that could be a great signal to Google that you don't want to watch such content.