I think the story is interesting because both sides really mess up. The Helghast kind of brought themselves down from causing conflict, but then it's the ISA/Earth's fault because they wanted to pretty much get rid of the Helghast by screwing them over after the Helghast uprising was quelled. That caused some terrorist acts by some Helghast, which led to very strict measures against them and caused them to pool their wealth to flee to Helghan. Earth and the ISA hoped that the Helghast would perish and continued to screw them over, which then finally leads to the events of the games.
In a way, I kind of feel bad for the Helghast because even though they started the chain of events (though that's because they weren't challenged by Earth until things went out of hand), they were pretty much neglected and expected to perish when they left for Helghan.
