I'm going to encourage people to report people who frequently make dark jokes to the authorities
Why do you want people to report them to the authorities?
Their jokes are so offensive they should be punished for them.
People have the right to free speech. You should tell them how you feel or grow a thick skin or ignore them and leave.
No I think if you don't agree with me that you are going to stand up for the rights of these people and maybe help me with the authorities then you deserve the same.
It can be upsetting to hear people make dark jokes but it is not illegal. The police are needed for more important things and cannot concentrate on trivial things like jokes.