In terms of Seattle you have two warring factions hell bent on destroying each other. Why though? Aren’t the Infected a big enough enemy? Why spend so much time, effort, manpower and precious resources on trying to eradicate fellow human beings?
Why, because they’re different. They’re the ‘other’. They’re a threat. We see this problem in the real world, where people who are different in some way are seen as a threat. To your way of life, to your families, to your jobs. Exist in your tribe and fear or resent or be indifferent to those of other tribes. The sad truth is both the Seraphites and WLF didn’t need to wage war on each other, both could’ve happily co-existed and in fact should’ve worked together in order to clear the entire city of Infected. Both had perfect bases of operation from which to work from and build safe communities for all. Notice one thing about the island? No Infected.
Jackson, albeit briefly, gives us an example of what is possible. Here we have a safe and functioning community where everyone has a role but all are working for a common purpose. It’s as a close to a ‘normal’ city as is possible in a post-pandemic world.
It’s about so much more than just Revenge Is Bad. If you can’t see that then, well, that’s your problem my friend.