Actually, ME, you had it right in the very last line. They prioritized their own needs and desires above the needs and desires of the rest of the universe. You know, kind of like the blood money I earn (believe me, it IS blood money) working for 8 hours a day 5 days a week in the summer doesn't just go to some charity, but goes to buy me books, or a new computer, or something.
So yes, if you accuse them of that, you're absolutely right. They prioritize their own needs over everyone else's, they fight what THEY believe in, not Durandall, nor any of his supporters. They want things their way, and when they can fight for what they want, they WILL. It's actually called BEING HUMAN, which goes back to my point to begin with. They're HUMAN, not demigods. They really aren't there too much for the world. They're there because they have a claim to stake that connects to them personally, especially after Darth Gichou probably (well, he did, but Kira never found that out with hard proof) sent those assassins after Lacus, and was undoubtedly trying to kill her after that.
So it's about Durandall being a threat to the CF personally that he had to die. The Destiny Plan didn't help his case either by getting the CF more evidence to come after him, and nor did his manipulation of sweet, innocent Mia. And Mia died too
. Bastard Gichou.