Dunno, I won't defend colonialism, but the idea that duking it out will resolve a border dispute doesn't seem likely to resolve anything. Yep, Europeans, mostly Western Europeans, drew the borders as they are. These borders are not at all perfect and the process by which they were drawn was brutal. However, nobody has ever done a better job of drawing the borders and actually having some borders is a good thing. In Africa for example, where the most arbitrary borders exist, they mostly replaced unmarked tribal territories. There wasn't much to go by here as tribes were duking it out in these areas since there were tribes, so it's not like there were some borders that everyone would agree on. These were also some pretty brutal conflicts, in tribal societies, between a quarter and two thirds of adult men die violently, making it by far the greatest cause of death. Arbitrary borders have their problems, but they're miles better than what came before them. If de-colonialism means letting people go back to fighting over who owns a particular piece of land, like Europe and, well, everyone else did for hundreds of thousands of years before borders were drawn, this doesn't sound like it matches up with most people's desire to just live their lives in peace.

I also don't think the core sin is gluttony so much as it's pride. Adding Taiwan to China or parts of Kashmir to either Pakistan or India wouldn't make their rulers more powerful so much as resolve an old perceived injury. Neither were even caused by simply by Europeans drawing arbitrary lines and had much more local origins. Taiwan was from the Nationalist forces taking over a very defensive position while Kashmir was from the Hindu dominated ruling class making a decision to join India that the Pakistanis and local Muslim tribes didn't like.