I think you’re confusing rationality for plain self-interest. If you have something to protect, then it may be reasonable to sacrifice personal comfort or even your life to protect it.
Also, you comment implies that the only reason you’d fight for something other than yourself is out of “liking the idea of yourself as some sort of social justice warrior,” as opposed to caring about something and believing you can win by applying some strategy. And saying you’d “ruin your life” implies a set of values by which a life would count as “ruined.”
A while ago, someone encouraged me read Homage to Catalonia, citing it as a book that’d dissuade people from revolutionary justice. And in particular, dissuade people from the notion that they should carefully guard who they work with, like a blue working with a green.
In fact, I found the book had the opposite effect. It describes a what amounts to a three-way war between anarchists, communists, and fascists during the Spanish Civil War. During that war, foreign communists and capitalists both benefited from continuing top-down company-owned business models in certain countries, and so strongly dissuaded a Spanish worker’s revolution, an agenda which Spanish stalinists cooperated with to continue receiving funding. The anarchists wanted that revolution, but were willing to team up with the stalinist bloc against the fascists, it seems, because they couldn’t fight both, and they saw the fascists as a greater threat. The stalinists (who did not want revolution) took advantage of the anarchists comparatively worse position to neuter them, rolling back worker-controlled factories and local-run governments, which were a threat to foreign interests.
The stalinist block would frame “winning the war” as a means to get the anarchists to surrender on all their hard won progress, saying, “well, we can fight over worker owned factories, or we can fight together against the fascists,” essentially holding the country hostage, using the fascists as a threat to get what they wanted. And in the end, they both lost to Franco.
This example seems to be a primary reason for not working with people who aren’t value-aligned: they’ll undermine your position, using the excuse of “unity against the enemy.” Once you give ground on local worker-led patrols instead of police, the non-value-aligned group will start pressing for a return to centralized government, imperially-owned factories, and worker exploitation. Give them an inch, they take a mile.
Moloch says, “throw what you love into the fire and I will grant you victory,” but any such bargain is made under false pretenses. In making the deal, you’ve already lost.
My model is that a blue and green working together would constantly undermine the other’s cause, and when that cause is life and death, this is tantamount to working with someone towards your own end. Some things matter enough that you shouldn’t capitulate, where capitulation is the admission that you don’t really hold the values you claim to hold—it would be like saying you believe in gravity, while stepping off a cliff with the expectation that you’ll float.