I have several theories on the recent feud.

Theory I

Somewhere along the line Sal and Richard have attached a "big brother" mantle on Artie.  The "big brother" label is only that because of the closeness in age.  Otherwise, it would be a father label.  For Artie (because he's normal), this is somewhat creepy.  He's saddled with two guys - two co-workers - who look at him as a father figure.  That's got to be a little tough for a guy whose mother still helps take care of him.

When Artie goofs on Sal and Richard, they see it as their father coming down on them, and they cry like little girls.  Artie - an admitted commitment-phobe - now has to deal with a relationship he wanted no part of in the first place.

I'd probably be angry too.  And, the only way to rid yourself of such a situation would be to get the two guys to hate you.

Theory II

Sal is dumb.  Everything he says is dumb.  He has no common sense.  Howard dislikes him.  Beth O dislikes him.  Artie hates him.  Sal's own wife hates him.

A person who eventually evokes hatred from so many people will eventually get a CD thrown at their head.

Theory III

Closely related to Theory II, and it is attributable to Howard.

Sal is retarded.

Some might debate the on air assessment that he is high functioning.

Theory IV

Sal is a genius and has manipulated Artie, Richard, and everybody in the studio and the listening audience like the great puppet master he is.  This is real theater that would make Andy Kaufman bow in awe.

This theory is of questionable status due to the higher probability of theories II and III.

(note to Sal: IV means 4)