What is it that allows people to make fun of something that is very personal to another?

There have been so many times that someone tries to tell others about a very personal experience and it really is something that touches their very soul and then others think it is time to make a joke of it? What is the answer? Is someone that views things different than another so less important as to hurt the feelings of the one asking? It happens all the time and it has happened to me what then?