Than continuing down the rails of the published adventure? Very probably.
There may be some people here who are taking a stance along the lines of "teach the buggers a lesson," but I don't think that's my position. To my mind, the execution/s would be the logical result of actions taken. If your PCs are negotiating with Lord Vetinari, knowing his reputation, and someone mouths off and someone else tries to kill Vetinari or take him hostage, a slow death in the lightless depths of the scorpion pits is a result; no need to play that out; extending the obvious and inevitable feels to me like the GM bullying the players, more than a couple sentences ending with "make new characters." The OP described the player of the character that instigated the fight in the chambers as "bored." Crapping on the game out of player boredom is close enough to asshattery for me to call it that, and it's something I don't have any patience for.
Yeah, the situation looks very similar to
DM: This dungeon door is trapped.
Player: I open it anyway.
DM: Make a new PC.
DM: This man is powerful, controls the legal machinery, and is known to be unstable and severely punishing of dissent.
PC1: I mouth off at him.
PC2: I attack him to take him hostage!
DM: Make new PCs.
The stakes were known, actions were declared, so consequences should be reaped. The DM can keep throwing softballs if he is intent on it, but isn't beholden to do so.