Does the author Matter?

In all of my English classes there seems to be some sort of background debate over whether or not the author of a piece matters. Some classes (and thus the professors teaching them) claim that we cannot get the full depth and understanding of a work of literature unless we can see where the author was coming from, what they were trying to say and the lives they lived before and after they said it.

The other side is that once the words are published on the page, read by a reader, the story is no longer the author's property. The ideas and images that appear in the readers' heads are their own, and not subject to post-reading adjustments from the author. If you didn't get that Dumbledore was gay, does that mean Rowling had to tell us at a reading of the book or does that mean that, if she wanted to get that concept across, she should have written it into the book better. Was it right of her to say that about her character or should she have left it up to the interpretation of each reader? To continue on a topic glanced on in class; does it really matter WHO wrote Shakespeare's plays and sonnets? Would the works have any more or less beauty, merit, poetry, or value if it was discovered that a woman wrote everything, or if Shakespeare was gay? Or if it was a ghost writer all along? No. The plays would still me masterpieces of literature, open to interpretation by the masses. The plays should have no less value or no greater value (though you can bet people would try to change that). I feel that an author can create characters and stories and make them however they want, yet they should also know that truly great works of art and literature can become greater than the authors themselves.