i don't think there is a definitive answer to this question, which is part of why this is such an interesting read!!
on one hand, the aliens have this incredibly perfect way of living. they don't kill one another, they trust each other, they are all patient and calm. but on the other hand, they only exercise this way of life by destroying another being's way of life. its one of those "do the ends justify the means" questions. i am inclined to say no because i think regardless of how perfect they are, the souls don't have the right to take anything away from humans.
it reminds me of the book "uglies" by scott westerfield (sp?) for anyone that has read it. there is one scene where the main character is thinking about what the world used to be like before everyone was made pretty, and she recalls that at one point people used to kill people for having a different skin colour, and she can hardly believe that was true. in her world, all forms of prejudice have been eliminated, but it only happened because all traces of individuality and personality have been eliminated. good outcome, bad means of getting there.
there are a lot of parallels between the two. sure, the souls have a "perfect" world, but the way they got there is horrible. i don't think the souls are really wrong, but they aren't good either.
the welts of your scorn, my love, give me more
send whips of opinion down my back, give me more
well, its you i've waited my life to see
its you i've searched so hard for