It is highly significant that just before the introduction of Caliban in Act 1 Scene 2, the audience is shown another relationship where Prospero has enslaved another character, Ariel. When the two characters are viewed side by side, there seem to be many similarities. Both are compelled to serve Prospero against their will, and both were formerly free before he came. When both try to defy Prospero, he threatens them with physical violence and/or entrapment. Both are forced to obey Prospero against their wishes. Although Caliban is much more vocal about his hatred of Prospero, it is clear that both Ariel and Caliban are far from willing slaves, and Ariel only obeys because he is promised freedom. Prospero tries to insist that his actions towards Caliban were always benevolet:
I have used thee,
Filth as thou art, with human care, and lodged thee
In mine own cell, till thou didst seek to violate
The honour of my child.
However, although he says this, and Caliban himself seems to acknowledge that at first Prospero and Miranda acted in a way that seemed to suggest friendship, these words are contradicted by the way that Prospero, even before Caliban appears, tells Miranda that the only value Caliban has is as a slave who works for them. It appears that Prospero contradicts himself, and that his reasons for enslaving others, both Caliban and Ariel, are ultimately more about how he can use them as slaves for his own benefit.
i thought the book was good and the way shakespeare described everything in the book was good too over all i enjoed the book
I wouldn't call it a love/hate relationship at all. At first they were nice to each other, Caliban welcomed them and showed them the riches of the island. After Prospero enslaved him, there's no show of love from either side. If I remember correctly, Caliban tells Prospero "I loved thee" (past tense) and Prospero to him "treated thee with human care" (again past tense). In the present, Caliban makes their (Prospero's and Miranda's) fire and brings their food (I.2) and does that only because he is threatened by Prospero.
Prospero's justification is in my mind no justification at all - it can be read as a justification only to relieve the conscience of the colonizer.
Politically, he conquered new land and brought his culture and language to the uncivilized creature living there. Any postcolonial critic would beg to differ.
Morally, he claims he had enslaved Caliban after he had tried to rape Miranda (that's Prospero's main excuse). But you could also argue that Caliban did that for revenge to both of them for "colonizing" his island. As Miranda said, she taught him their language and Caliban replies his only profit from it is that he knows how to curse. He doesn't want their culture, he doesn't want their languge, all he wants is his island which was rightully his and taken from him.
So I would say I very much question and reject Prospero's justification behind the enslavement.