Not that we're doing ourselves any favors, leading them into an ambush. I just don't think we have enough chips to fund a winning gamble at this point. My idea would be to recruit more allies, either in this world or the next. If we take Kasen and the rebels and escape, we can go recruiting, and choose from rebellion, sedition, propaganda, etc. If we steal the boat, we can recruit some hags for a hax win. Either way, escaping Sombrero with our party intact seems more important than defeating him.
Also, "hammering on that enough will eventually bring them to their senses." I just don't see it happening.