Reading my comment as moralizing and not being matter-of-fact is imho pretty naive, no offense.
Let me put it in another way. Monsters and sentai don't exist in real life. Workplaces and colleagues do. When the team leader of a project fucks a coworker on the down low to keep her motivated, what happens is usually this: the projct churns along for a while, then the office affair inevitably gets found out; breakdowns and backstabbings ensue; the proect fails, lucky/well positioned wokers get reassigned, unlucky ones get fired.
This is basically what they teach you in management classes: a manager that would prioritize keeping the situation hidden for the project success over separating the couple the second they catch wind of it would simply do a bad job. True for accounting offices, true for world peace.
No offense taken, since you're still just moralizing at the core of your argument, lol. Ironically, you're even further making my point. Monsters and Sentai don't exist. But workplaces obviously do. This is why it's entirely pointless to view it through the lense you're viewing it in and hyper-fixating on something as stupid and common as an affair within the context given to you. Because it makes even less sense to do so if you approach it matter-of-fact. As hilarious as it is to try and bring "management classes" and HR into the scenario of a fictional sentai team manga, even if we humor analyzing it from that perspective, it's clear that any management class should help you understand why
making Red quit in a scorched earth all or nothing method is a really, really fucking dumb idea.
When faced with saving the world, team cohesion should trump the need to forcefully dismantle the team based on something as insignificant in scope as an affair. It's common fucking sense. Priorities exist. In life, we sometimes must work with people we don't agree with or who do things we don't find palatable.
It's called being an adult. Furthermore, it's not even like there's three team members involved in a triangle that would strain actual team cohesion. It's an affair between two willing participants. Blue trying to destroy the team based on something that doesn't immediately affect the team is ridiculous, and jeopardizes world peace for literally no immediate gain. In fact, it quite literally destroys the team (two will likely die), and it diminishes significantly any real chance at saving the world (everybody dies). The consequences of removing red are disastrous for them. This should be dealt with carefully, and most importantly,
much later. In otherwords, being pragmatic calls for the opposite of what you're claiming is pragmatic. What it really is, is just moralizing nonsense that
doesn't intelligently weigh consequences. Any "management class" would give you a failing grade. As I said, it is not worth killing off the team, and forsaking the world just to "do the right thing."
That's called being naive.