Kingdom Hearts II Can somebody help me understand the story?

Hey I need help understanding KHII. Here is where I need help on the plot. Is this it?
After the slumber Sora, Donlad,Goofy. They arrive at Twilight Town and Meet Hayner and the gang. Soon the ride the trian to Yen Sid Castle and find Pete. Pete tells them about him and Malificents plan of conquering the worlds. Sora doesn't belive him ofcourse beats his heartless and enteres the castle. Soon they meet Yen Sid. He tells him that their is still darkness in peoples hearts and then explain about the Nobodies.Then he tells them about Orginization XIII and they are set on a goal. He tells them to go and figure out their plan and stop it also they need find king mickey.After all their searching they find king mickey and learns that the Ansem that they defeated was a fake and the real Ansem Mickeys freind is still out there. He tells him the Fake was Xehanorts Heartlees an aprentince of Ansem who betryed them and turned to the Darkness. Soon they figure out the leader of Orginozation XIII Xemnas is Xehanorts Nobody and that they are using Sora to destroy heartless and gain the hearts they have captured to make their own "Kingdom Hearts". Sora with his freind Riku most defeat Xemnas and stop his plan of making Kingdom Hearts.

Here are my questions about this.

1)A user told me that Sora wants to beat the orginization not because what they are going to do after they make KH but the WAY they make it. What is so wrong with the way they make it? Does it turn the worlds into Darkness or something?

2)This is all I know on KH2 if you have answered 1 please give me any additonal info I might need to know.(Oh I already know the ending and what happend I beat the game I just wan't to know why sora needs to kill the Organization thats all.)

 

Let me clarify: (By the way, remember to put a space between sentences)

1) Orgainization XIII is so desperate to get back their hearts that they are willing to do ANYTHING to retrieve them. That includes murder, stealing hearts, mass murder, trickery, etc.

2) Sora needs to wipe out Orgainization XIII from existance because they'd clear out whole worlds to get back their hearts.