Guess Who?

Do you know who I am?

I’m a man. I’m a world figure. Some people love me. Some think I am the Anti-Christ.

Wherever I go, crowds follow me.  They cheer me on. They yell out my name.  Rock stars sing for me. People pay careful attention to what I have to say. My words in Washington were listened to by people all around the world. My books are bestsellers.

My mission in this world is to help save it.

Who am I?