Patents don't need to be safe. You can patent a transportation device that works by firing a human out of a cannon, or a self driving car that simply runs over pedestrians, or even just a method of killing someone.
Can I patent a self driving car that runs over pedestrians so that I can sue any company whose self driving car does it that hasn't paid me a license fee?
https://pbs.twimg.com/media/EzmEZ9oXEAQOiY1?format=jpg&name=...