What music did Sondheim "steal"?

I am in an on-going debate with my music teacher. We both love Sondheim. I love Lloyd-Webber, but my teacher hates him and claims he "steals" all his music. I believe that you can't "steal" music; there are only so many notes that you can put on a page. So far, I've figured out that "God That's Good" from Sweeney Todd is almost exactly the same as "Some Enchanted Evening" from South Pacific. Can anybody think of any more examples?