The Joined could still be individuals

(TL;DR if I had the perspective of every person on Earth, I'd probably be voluntarily acting like the Joined. I find it hard to believe that you would not, too.)

The freedom of choice is not necessarily taken away from the Joined.

All we know is that the Joined itself consists of the collective past and present experiences of approximately 8 billion people.

When you are struggling with a difficult problem and you ask for someone's advice and eventually take it, have you lost your individuality?

Apply this at a larger scale: when I, as a member of the Joined, have the thought "maybe I should stick these razor blades in this halloween candy," I can recall every experience of pain, sadness, and distress caused by similar actions. No person, when presented with the real and tangible empathy associated with this misdeed would act this way.

In the same vein, think of the pain of starvation. Necessarily, given the experiences of every person to ever suffer, how could one stand in the way of the stockpiling of food?

Even the question surrounding starvation can be ascertained morally - the most sustainable life possible for humans would be one of minimal intervention, allowing the ecosystem to naturally heat over the sun's lifespan (at least one billion years of livability on Earth). With the understanding of providing a better future for their young, I don't think it's far fetched that the elderly would sacrifice their bodies for the lives of their children. You gotta think BIG.

As for the biological imperative: at the rate we're currently going, humans will render the Earth uninhabitable. The rapid warming we are experiencing is an existential threat - undoing the pairing (?) reintroduces that threat. (look up the Great Filter).

Being OK with giving a nuke to Carol is wild, but I don't believe it would amount to an existential threat. I am sure there exists infrastructure across the world that would allow humans to survive nuclear fallout. This, I would say, is the weakest point in my analysis regarding rational choice. The idea of putting the happiness of one above the safety of all seems counter to the show's utilitarian presentation of the Hive. Again, this may be only because, rationally speaking, Carol and the unjoined are a blip in what will be a millennia of peace. May as well increase her happiness while she dies alone?

Me? I'd probably Join. The allure of all of that knowledge and experience sounds amazing! Even if my body is physically doing something mundane, I could theoretically be participating in such amazing discussions and advancements. How cool is that?