Language Thoughts
Swearing is shorthand communication.
The fact that the swears are present, indicates a significant set of emotions (anger, frustration, irritation).
Packed into words like "asshole" and "jerk" is a batch of communication about the character of the person under discussion.
Words like "shit" and, in overlap, "asshole" represent that which causes disgust and disease, endless troubles.
Each word has its own history and fairly specific application. You wouldn't call an irritating person a "piece of asshole" nor does one often call another "shit." You might call him "a shit" or a "shit head" and so on, but it is (in my experience) rare that you simple call someone "shit" as in "you are shit." But those lines are blurring, ALA "fuck you, you fucking fucked fuck" - verb, gerund, adjective, noun.
The construction of the swears transmits information, like any other language, and the delivery/body language are part of the communication.
My theory for the day: when swears become so overused that they are part of a person's normal vocabulary, it becomes difficult to express emotions about and criticize the character of someone without resorting to something stronger, like threats and violence.