Ah, this thread really does fly. Some arguments were presented.
-Telling the King and Kragg will only lead to shame about the Dark Dwarves:
No. Full stop. That's strategic level information. It will not lead to "only this one thing" that favors the way you want people to vote. Let's be frank and factual about this.
1. The Dark Dwarves are a shame upon the dwarven people. But if anyone among the dwarves can deal with that shame, for whom it is an old and familiar one, than that's Kragg and a dwarven King. Espetially the King who is trying to reclame a hold a lot closer to the dark dwarves than most of the holds. Will there be shame? Not more than there already is.
2. The Black Orc creation thing. That's strategic level information. Its the origin of a plague. You know how plagues work? Right now the Black Orcs are considered just another mad thing in a mad world. They can't even make a grudge over them, because they just popped up. Having someone to blame for it will only help. Because now they can make a Grudge about it, instead of thinking its just a mad world out there. Grudges they can understand, and eventually, deal with.
3. "A grudge against the dark dwarves is a bad thing" argument. No, no it isn't. There is already a mountain of Grudges against them, not least for abandoning their Gods and all their crimes since. No, the dwarves wont suddenly harry off to kill them all. The primary trait of dwarves is patience. Like the lost Karaks, they'll remember. And plan, and plot. And when the day comes when they can do something about it, then they'll act. And don't tell me this one, this one Grudge, will be the one that breaks their back. No it won't. Grudges are how the dwarven alien psyche deals with these things. It's normal and natural for them. It just goes on the list of "things to deal with, when given a chance/eventually".
4. Telling them Wizards can be possessed by Mork/we were possessed by Mork. Fair, but that's not the whole story, now is it? The story isn't "oh this human got possessed and gave up and now its a risk" its "She got possessed and her ancestor gods stepped in and bleed the fucker". If anything its encouraging. Humans can get possessed is not new information: See Norsca, Chaos, Chaos warriors and Chaos Warriors and Sorcerers exploding into deamons. This is not new information. This part of why everyone is allways wary around us, and why every wizard is vary of magic. You are not tellling them a new thing when you tell them wizards can get possessed. You are telling them a new thing when you tell them you robbed fuckcng Mork.
5. Again, we committed Grand-theft God. This may matter. As multiple people have posted, it could be anything from "Uniting the Orcs and Goblins remaining in K8P" to "Here, have another Waaargh, just for you". The King needs, needs to know a God got robbed in his home. If a Waaargh comes in later on because of this, because of us, and they aren't ready, everything we've worked for here will be undone. That's strategic level info they need to have. Rangers need eyes on the wastes, now.
6. Talking about the dark dwarves with them is a prelude to talking about the dark dwarves with the Grey Order. They might know about them, but few places are likely to know as much about them as Kragg the fucking Grim, and knowing more about the enemies of order is a good thing for the Empire. Even if they are "Way the fuck that way". If nothing else, we can warn other Grey Wizards about it, and not to bring it up. Keep in mind, Mat told the Colledge she was going to dwarf town, and no one mentioned anything about dark dwarves. So either to Colledge doesn't know, or for some reason decided not to tell her, even with mind spells on hand, like for the Skaven. And I don't know about you, but I think the Colledge needs to know about another kind of dwarf, a dark one, before their merchants, traders and other agents abuse the ignorance.
In conclusion: Talking to them about this is risky. Yes. But it is worth it. At least to me. We've seen that 100 roll for the Grenskin response. They were united before the headlong charge. They might yet be again. God alone knows what might be coming from the wastes. They need to know a God was pissed off. And a lot of the talk about possesion was kind of misinformation. Wizards getting possesed is not a new thing. Its part of the reason they are so feared, and so disapproved off. At least this time we can point and say: Yeah, but my Ancestor God came in and wrecked the fool.
EDIT: And ok fair, its entirely possible Mork just fucks off. But that's just a different kind of gamble you are talking. There are no safe options. Just picking your risks. Welcome to Warhammer.