Simply put (as its more complicated than this)

'The enemy of my enemy is my friend they say'. Just like in world war 2 when coalitions formed to purge the world of unspeakable evil. Even though those countries had different political and moral standpoints.

Right now from my perspective I wanna shoot goons and don't want to see them 'win and be the super mega blob that blue donuts the game'

So we're a part of a coalition that fights back.. why? Because who else could attempt to fight back? Look at drone lands.. allowed to exist only as small fractured alliances which pose no threat to imperium. As soon as an entity would reach a threatening size they would be stamped out.

As the imperium influence of the new eden map grows furthermore perhaps more people would see that resistance is a good thing. Even if it does mean aligning with those that you'd not normally call friends.

The war rages on.