why would the goal be to get him booted out of the relationship just because I don't see eye to eye with him?
You and I actually agree on this. My points don't really apply to you, more to the OP.
No, I wouldn't personally want to boot someone out. But a lot of people go into this-- this is from talking to friends in the poly community-- thinking that they can just bring people in and kick them out with no regards to that person's feelings OR their partner's feelings. As if their "relationship structure," or whatever you want to call it, is some kind of Mr. Potato Head, where you can just pop pieces in and out as you like, depending on your mood. And that can get very dicey....
You knew what you wanted and created an environment where you don't have to worry about that, but not everyone is that secure when they start out in poly.