If you were replaced by an alien pod person who was identical to you down to every molecule on every strand of your DNA -- what would be the difference?

Most people know the basic set up of the story Invasion of the Body Snatchers: alien pods land on Earth and grow into copies of existing people, then eliminate the originals and take their places. According to the story, the alien pod people are molecule-for-molecule identical replacements of the original humans, so what’s the difference? Why not just shrug and say, “Big deal”? If the replacement is exactly like Uncle Elmer down to the placement of every molecule in every strand of his DNA, why not just accept the replacement as Uncle Elmer for all practical purposes and move on? If you are replaced by an pod person who is identical to you — so what? Every movie made from Invasion of the Body Snatchers has proposed a difference: the alien pod people are EVIL! The pod people have evil plans, and their takeover of the human race is an evil plot to commit evil deeds. When pod people look at you they have evil facial expressions, and they speak with evil intonations in their voices, and stand in evil shadows, maybe lit from below with green light. Sometimes the camera tilts to one side when pod people are being photographed. When a pod person walks into the room, the theme music gets atonal, and maybe goes into a minor key. In other words, every movie made from Invasion of the Body Snatchers has completely missed the point. In the original book by Jack Finny, the pod people aren’t evil, they just want to be left alone. If they’re discovered and they strike at humans, it’s only out of self-defense. According to Finny, the pod people really are exact copies of us except for the one quality about humans that can’t be duplicated by purely physical means: our attitude. True human beings care about what’s going on in the world, and want to make a difference. Pod people don’t. They only mime caring when there are true humans around to fool. Once the true humans leave the room, the pod people go blank and sit on their sofas all day, staring at the wall and honestly not feeling any need to do anything beyond that. The pod people are just like us except they only exist, they don’t really live. If the alien pods succeed in completely replacing the human race, they won’t do anything overtly evil. They’ll just let everything we’ve created eventually fall apart out of apathy because no one cares enough to create anything new, or maintain what already exists, or try new things. To Jack Finny, a world full of people who don’t care one way or another was a lot scarier than a world full of people who are flat-out evil.