I was recently asked why it is that some people tend to enjoy joking about dark and disturbing subject matter. Here is my .02
Well there are a lot of reasons people are attracted to dark, disturbing, or violent imagery and discussion. It varies from person to person, from moment to moment, and is subject to change.
1. Yes, it could be that the person has disturbing thoughts and jokes are the only socially acceptable outlet for them.
2. It could be for shock value, interpreted as cool or edgy, and the person may be expressing themselves that way in order to portray that edge, much like a way of dress or smoking can be done as a method of expression.
3. We all have a "shadow" to our personality. We used to be able to express this through our own means of living - blood, guts, feces, and death were a part of everyday life. Sex was taboo, but death - that was just part of life.
Now, it's quite the opposite - very few of us have actually killed an animal for a meal. We have toilets, bathrooms, bedrooms, privacy - unless you have siblings, it's very likely you may have reached young adulthood without ever seeing the opposite gender nude. So, we have a lot of stigma associated with the blood, guts, gore, feces, and death that were previously part of everyday life. When someone died, you put them in the parlor for 3 days, let everyone give their respects, then you buried them. And you went into mourning for a time where you wore black and didn't attend social functions. Then, when your period of mourning was over, you were permitted to wear color again and rejoin society.
I think it was in the 1920's or 1930's when a popular woman's magazine stated that it was unfashionable to display a body in the home. Families were encouraged to set away their heirlooms and replace the family parlor with the "living room". This created the funeral parlor. Also, with the increase in medical care, more people were dying in hospitals than at home, both death and the body were no longer something to be dealt with inside of the home. As time went on, sanitation improved, houses got bigger, privacy increased, meat was killed and butchered by the butcher or farmer rather than members of the household, and medical care improved. We were living longer, healthier lives. So, as time went on, our exposure to the core, essential elements of living were restricted to the point where it was considered rude and crass to even discuss them.
But, they are part of our existence. A part that we are no longer exposed to except in small, restricted amounts that we are no longer permitted to acknowledge. If the thought of blood, feces, or puke turned your stomach you wouldn't be very effective 60 years ago. Now, it's perfectly acceptable.
We are no longer allowed to grieve properly. It's no longer acceptable for anyone to be sad over someone's loss, we just tell them that the deceased is in another place and that they should get on with their life. As a result, we force people to hide their grief and internalize it, and as a result they hang onto that grief rather than letting it out and working through it.
So, we have essentially turned these topics into social taboos, and that causes us to ruminate on them. It creates a shock value and creates a need to explore our feelings towards those topics, yet we know we are not socially permitted to discuss them.