[MENTION=18701]Oryan77[/MENTION]
Implement "King Ball-cutter" as soon as possible, like next session. And make sure he (or she) is significantly more powerful individually compared to any PC. Better yet, use an NPC authority figure theyre already familiar with who knows the PCs tactics/abilities. If you need a hand building the NPC let us know, ENWorlders like making monsters
Run the one-on-one challenge, let the dice fall where they may, fight smart, and be unremittingly BRUTAL.
Heck, you don't even need to wait for one of the players to make some insulting crack, just have them meet the NPC on his home turf and have him bring up some of the insults, as in, "Ah the headstrong adventurers. Tell me, what was it you called me last you were in my throne room? My jester has seem to forgotten the words." And his jester is there pleading with the King not to make him tell the asking what the PCs called the King. If they're the type of players you describe, they're sure to lay into the King with some more creative insults...
If the loudmouth PC doesn't respond with "I submit, your Majesty" or something similar, have the King coup-de-grace on his balls and then behead the PC. He'll then order his knights to burn the body to prevent resurrection, and turn to the rest of the PCs, "Now, can we get back to business, or are there anymore of you who would like to demonstrate a lack of due respect for your King?"
If the PCs decide to attack all out as a party, have very hard opposition prepared with court mages, great weapon knights, crossbowman on the overlooking balcony, maybe a pet dire wolf or bear, plenty of footmen, etc. If the party succeeds and kill the King, they are labeled "Kingslayers" and will be belittled as such wherever they go; and if the King was essentially good and this was all an ego contest, they've destabilized the realm so real evil can enter the picture...maybe alignment changes are appropriate too. If they fail to kill the King, have the King execute the most aggregators foul mouths on the spot, giving the remaining PCs an opportunity to show due respect or be slain and their bodies displayed as a warning.
IOW, if they only respect force, give them the %#€@ hammer of the gods and make sure they never forget it.