One cannot decide if Prospero is a protagonist or antagonistic based on his actions. Neither can we determine whether Caliban is a victim or a foe. Shakespeare raises a very important social question for people of the Renaissance, one that is still valid today, "Should we forgive the actions of those less fortunate than ourselves, simply due to their handicap?" As the play progresses, the audience shifts their opinions back and forth about Caliban as a foe or a victim of Prospero's harassment. They must constantly struggle with whether Prospero is only protecting himself and his daughter from an evil villain, or whether he is himself a "bully" picking on one who is less fortunate. Shakespeare wished to make the audience uncomfortable and create an inner struggle in them. He engaged that audience as a participant in the play, rather than as a third party observer. This is evidenced by Prospero's plea in the end that he can only be freed from the Island by applause. The issue of Caliban's physical disability is often ignored by critics who attempt to categorize...

However, in order to understand the true intentions of Shakespeare, we must look beyond the actions of the characters, and take a real look at our own perceptions about how we feel when we look at persons with a disability.
Everyone wishes to believe that they see someone with a physical disability as an equal and that they do not view them differently. Yet, when we watch the evening news and see a handicapped person commit a crime, we question whether we should punish them the same as if they did not have the disability. This is especially true if the person has a mental disability and they may not have known right or wrong. This is the same effect and response that Shakespeare created in the audience with Prospero's treatment of Caliban. No one will disagree that Prospero is self-serving and arrogant about his powers, but the real question is whether Caliban was a deserving criminal, or whether Prospero should have "gone easier" because of Caliban's physical limitations.

References

Shakespeare, William. The Tempest (Norton Critical Edition). Edited by Peter Hulme and William Sherman. New York, New York W.W. Norton and Company. 2003.