You laugh at comedy or humorous scenes when you see them in TV shows, movies, comics, etc. There are number of situations that can cause laugh in a human being but the reason behind all of them is very common.
Remember your last episode of Mr. Bean you saw on TV. It is obvious that if you have laughed at many things in it. And I bet the mostly the situations you laughed at, will be situations when Mr. Bean hurts somebody or something, somebody hurts him or he hurts himself. So what should I call you? A person with good taste of humor or a sadist who laughs when some one gets hurt or insulted?
Do you feel pity when somebody around you falls suddenly, or you laugh at him? This is what we call it as a human nature.
Even, when you see at the shows of mighty comedy king Charlie Chaplin, you will notice that something bad is going on with the characters and you are enjoying laughing at you heart’s content.