As I'm stating (like four times already), Sasuke could keep silence without giving them any information. I don't disagree with Sasuke keeping the information for himself. So stop saying that we don't agree in this point, that's perfectly rational if you ask me.
The problem is other:
- He treats them like fodders
- He says he is directing, and that they can't do anything, hence they don't need to know what's happening
- ...and after Naruto's speech, Sasuke speaks
Sasuke's course of action in that situation could mean death for Kakashi and Sakura, and by transitivity for Naruto. Why? Because from now on, if Kakashi and Sakura were not members of Team 7, they might consider not following Sasuke's direction since he doesn't have touch to socialize with people, ergo, he is not charismatic, Sasuke wouldn't convince people to do something. In the case of Naruto, Kakashi and Sakura not being members of the Team 7, Kakashi and Sakura going outside of the Susano would trigger Naruto going outside to save them and thus finishing the war.
We could see the situation in three variations.
1) The current case: "They don't need to know since they're powerless, but then Sasuke tells them".
Bad move. Very pragmatic, but extremely risky considering the presence of Naruto.
2) The case of staying shut: "Team 7 members wouldn't act without information and Naruto could stay collected".
3) The case of speaking without objections: Members of Team 7 would have the information as case 1, but Sasuke would be more charismatic, thus being more trustworthy and could lead with more ease the team.
As I said earlier, your description of the need of assertiveness is almost correct, but you're only seeing this in the rational way, a theoretical point of view of a shinobi. But you're not being contextual, as there is also an idiot like Naruto in that place. Any wrong move and Sasuke could force a bad reaction from Naruto's part. That's where leadership comes to be an important factor.
The point is, Sasuke has always been arrogant, and let's face it, there is a maw of difference between their powers. It's just a fact and he has always been vocal about it. He probably lashed out at Sakura as he has - together with Naruto - saved her how many times now? It's important to tell her her place as far as the war tiers go. She's weak and now, quite frankly speaking useless. His words are harsh, but they ring with truth. Sometimes, it's important to tell people the truth no matter how harsh it may be.
If he doesn't, she might rush outside again, ruining everything. So, it's important that he stresses her position and same is the case with Kakashi. Why should he remain silent, when the chances of them trying something stupid are colossal? That way, Naruto might go out and ruin things, putting the whole world in jeopardy. It's no time for etiquette man, but straight responses.
I will not agree with your second point at all, and my post covers it mostly. Not telling them means they would make rash decisions. Remember Sakura rushing at Madara for no reason? Even if he tells them about Limbo, they won't understand as they cannot sense or see it. So, there is no point. What the better solution? Tell them bluntly that they're useless. The shame would instill the gravity of the situation.
Remember, there are times when harsh language is most effective or even punishment. For example if a 4 year old starts to cross a busy road, it's recommended that he should be punished with a tight slap. Why? Because parents will not get another change to reinforce his behaviour. Sasuke may not be a parent, but he can see Limbo, he can recall viable information, which Naruto again failed at: "Who is Kaguya?" This means, the guy isn't that reliable in this department. So that leaves him to reinforce their behaviour with bluntness.
Sasuke is a prodigy and can easily take Kakashi's role, but can Kakashi do the same if he isn't told that he is useless? Keep that in mind that there is nothing stopping Kakashi and Sakura to do something stupid, especially the latter. That would galvanize Naruto into action, making him do something utterly preposterous in turn, and if he's killed then what?
The situation is too delicate for pleasantries, I'm afraid. Far too delicate, as it's not a matter of one nation, one country, but the whole world. Why should Sasuke indulge them is beyond me. Bluntness is the way to achieve the best results here. That's all I'll say.
Sasuke needed that line about becoming Hokage a lot more than Naruto did. Dude continually fails to realize that he can't seriously act the way he does and expect to become Hokage. Even Danzo knew that the perception of others mattered.
Because, that's obviously how Hokages achieved their merit - through the opinion of every citizen. Democracy, correct?
