You don't. If the group is too strict, you find another one. Having no borders would sure help.
But yeah, global issues need a global consensus. Can't let someone kill the planet for all of us.
Non-interference unless what an individual is doing obstructs good of others. Includes the expenses if they are high enough. This cannot be defined individually.
And, 9/10 times between mutually aggrieved parties there is no shared definition of aggression.
So, no, it's not that easy.
To paraphrase Fred Brooks: "Show me your arguments and conceal your definitions, and I shall continue to be mystified. Show me your definitions, and I usually won't need your arguments; they'll be obvious." (s/flowcharts/arguments/ and s/tables/definitions/ from the original.)
Insisting that everyone in the room uses the same definitions for all words, and trying to force some mono-mind of language, rather than actually working to solve problems is counterproductive. It can be productive to discuss and understand how terms are being used differently by different parties, and it is absolutely necessary for everyone in the room to understand that words are different for different people, but then you have to actually start working on the shared problems.
It's incredibly frustrating when people waste everyone's time trying to come up with a completely new shared "compromise vocabulary" that no one is happy with and will get discarded the moment people leave the room.
As a non-political example, the first time I heard the term "server-side rendering", I thought it was one of the soonest ideas I had ever heard. With the latency between client and server, needing to go back to the server for every screen draw would make for an incredibly laggy interface. I hadn't known that JavaScript developers use "rendering" to refer to making HTML, whereas I associate it only with making an image to be displayed. Because there was no shared definition, communication was harmed.
Solidarity is when people who substantially agree on something act in concert.
I can't see how one can substitute the other.
People have been doing it since "at least" the French Revolution, I am sure that you could chuck some Pericles speeches in there too
This reconciliation is embodied in phrases like, "I disapprove of what you say, but I will defend to the death your right to say it."
Solidarity is not conformity. You can be different. There is likely no person on this planet with which you truly have no shared interest, no shared objective, no shared sympathy. Even if you find you identify strongly with your difference with another, the ability to see more fundamental shared interests, objectives and sympathies are the underpinning of things like secularism, freedom of speech, and liberalism in general.
On the other hand, going a little further with that phrase: "I disapprove of what you say, but I will defend to the death your right to say it." - while it's a benign ideal, looking at applications of that philosophy in practice you often seen it being applied in an inconsistent manner, whereby someone's "right" to say someone infringes on the autonomy of others (essentially a case of competing rights). It's only in cases like that where individualism comes into play.