I think to the contrary - the amount of invective in the US political discourse, especially on the net is intolerably high. Most of it is the name calling of the lowest possible order even in the world of insults and sets the US males well below the international "standard" (if there is such a thing). I once inadvertently participated in an exchange between Indians and Pakistanis - the level of insults was quite high, but there were few personal invectives of the "fuck you" variety - most of it was making fun of each other customs and religion.
By comparison, the exchanges on this list are for the most part civil and that is, imho, one of the main attractions of this list (the other one is the level of participant's knowledge). So I am with that list member who complained about the level of invective.
Wojtek