There's no logical reason that some words are "bad," but that just means it's arbitrary. Since all of language is arbitrary, it's really impossible to just criticize swear words with an arbitrary negative connotation. Lots of other words have different types of emotional connotations: e.g., cute vs. hot. What do you think of when you hear the expressions "to fuck" versus "to make love"? The meaning can be the same, but lots of words, not just swears, have an emotionally-charged connotation.
I do think it's ridiculous to get offended by a swear, but all social constructions are arbitrary to some degree. Why do you wear clothes in the summer? That nakedness is inappropriate is entirely arbitrary. But these constructions still can warrant following if you want to function in society and have a basic level of respect for other people's sensibilities. For instance, my grandmother thinks excessive swearing is rude, so I don't swear excessively around her.
