The excuse about forcing this marriage because you don't want the ogre factions to spilt is pretty dumb since they technically are already spilt and not much is holding them together in the first place. It doesn't help that the main crew know their being hunted by some very skilled humans but are just letting the shaman drag them along because reasons.
They might be technically split already, but officially they're still united as one ogre community and, most importantly, are not currently having a civil war and killing themselves. Saban's faction evidently has a lot of power, and therefore a lot of leverage to get what they want. Telling Saban to piss off would be cathartic but without a united front they'd all be more vulnerable to the humans, so acquiescing to Saban's demands is the lesser of two evils for them.
Being able to decisively break such a status quo would take some serious protagonist power...