One reason is that bad words are frequently known by more people therefore more ‘common’ or ‘base’. I could say, “That woman has a nice ass.” and everyone would know what i am talking about but if i said she were callipygous, eyebrows would be raised for a different reason.
I also think that swear words are more primal and thus remind us of our animal origins which some people would rather forget. Think of how many swear words relate to bodily fluids and functions.
I wonder if I could expand on your question and ask anyone–Do you think that the other forums are necessarily better or more intellectually stimulating, because they ban certain words? I personally think that intelligence manifested in responses or questions is not measured by how much or how little censorship there is. I mean I almost always believe that a person should be allowed the most freedom possible to express his/her thoughts in order to further develop intelligence. What do you all think?