Google and Scientology seem to think that putting the Scientology ads on pages containing certain keywords will pay off for Google and YOU (if it is your pages) better than other adverts.
Is your problem that you just don't like Scientology. So what? Let them pay for your space.
Is your problem that you are a fan of some competing wacko religion such as Christianity? By all means have the adverts taken down. I'm always glad to see wacko Christians make less money.