It really isn’t that fucked up. They aren’t actually experiencing the trauma, they are just laughing it off (as opposed to laughing at something as a way of dealing with and moving past pain). Not because they are cruel, but because its easier than thinking about it. We do it here all the time with the news puns because the things are so distant they don’t really impact us. One would hope that they would show some sympathy since their friend did experience it, but I guess they are just asses.
If this had this impact on you then you obviously don’t really hate the world. Just like most of 4chan doesn’t actually hate the world. They would react to actual trauma in their lives just like normal people. It’s just that most of them are kids, and teenagers all act like sociopaths all the time. A person who really hated the world would have reacted to this with a happy feeling that there are two fewer kids in the world and they would have relished in the woman’s pain. They wouldn’t have been able to pull their gaze away because they would have been enjoying the outpouring of anguish.
The point being that no amount of fake shock seen on the internet will actually desensitize you to something terrible actually happening to you.