Saix tells Sora he has Kairi and he can't see her so he will continue to world-hop and take down more heartless. Since Roxas's keyblade can't do it anymore because he left they have to put Sora through manipulation to make him do it.

And it's true that Saix was a bastard, and hurt a lot of people just to get his heart...But Sora killed a lot of people just to keep him from his heart too. Aren't they doing the same thing?

Xemnas even says "Light and Darkness are eternal, so why do you hate us who are caught in the middle?" Now I'm not saying Xemnas was a good fellow, or his actions (or any of XIII's) were justified, but it just seemed kind of...mean to me that Sora didn't care at all. Even when Sora asks him "The heart isn't all about hate...it has a lot of emotions. Don't you remember?" And Xemnas looks sad and says "Unfortunately, I don't..." Similar to Saix stating he only wishes to exist and staring at Kingdom Hearts while saying "Kingdom Hearts...where is my heart?" I guess I thought that was pretty sad.

Also, when you defeat Finkelstein's experiement, Sally says it did the things it did because it wanted a heart and didn't have one, and Sora says "When you put it that way...I feel kinda bad for it." But not Orga XIII? Are they not the same?

Anyway, it's not like I disagree with you that XIII didn't need to be stopped, they didn't need to do the things they did, they were very ebil people who went out of their way to torture others... But they do have a goal in mind, and that's to exist. So to say they did horrible things to get their heart is the same as saying Sora does horrible things to keep them from their heart... He's killing them just like they are killing others... That's how I took it anyway.. But it's all just my opinion, so...