This is not the case. Humanity is bent towards evil ans destruction, in that people only behave morally and do good because they fear the consequences and the established governing authority. People do as much evil as they can get away with and behave wickedly when they believe that no one is watching them.
You forget something here.
Noone (or almost noone) does evil things simply because they are evil. They do those things because they think it is the right thing to do. Or they think the gains outweight the sacrifices.
To come back to the nazis: the true beliefers in that ideology beliefed that the "lesser races" had to be eradicated for the good of humankind. They didn't think "I will kill them simply because I can get away with it."
The same goes for almost every criminal.
Do you lie when you can get away with it?
Counterquestion: Do you lie whenever you get the chance to lie?
Furthermore is lying always evil? Is it evil to tell a person who's dying a lie to make their last moments of their life more bearable? Is it evil to lie in order to save an innocent life?
Apart from being a matter of point of view, "good and evil" are also a matter of circumstance. An action that is evil in one situation can be the right thing to do in another.
Just look at the invasion of the GTVA. The GTVA think it is the right thing and it will save far more lives than it will end. The UEF thinks it's evil and done out of egoism and intolerance.
And the beauty of it is, you can't definately say which side is right.
Okay. Topicchange:
As much as the UEF culture is pasifistic, they still retained a quite effective military nontheless (not comparable to the GTVA maybe, but still far stronger than the old GTA ships). So I don't think they are "suicidal beyond rescue", they would just need a little nudge in the direction the GTVA considers to be the right one, to become able to survive in a universe filled with enemies. Total subjugation is way over the top if you ask me.
And to those who think the UEF need to capture GTVA vessels to get their hands on beams, remember the defections of the Orestes battlegroup! Among the those ships was one Anemoni (or somesuch) Logistics ship. Since those are build to repair all the other ships in the fleet they are bound to have replacements for beamturrets destroyed in battle on board or at least enough spaceparts to build new beamscannons.
And they have crew proficient in maintaining and repairing beams.
So the UEF will have the knowledge to produce their own beam weapons in time, no matter if they capture any more GTVA vessels. The questions are, will they be finished in time and can they be fit into their current vessels?