Fan Fiction and Originality

There are people... including some fan fiction writers... who say that works of fan fiction are not original, because the writers thereof are building on someone else's material.

Well, I do not agree with this. Yes, we are using material originated by others, but we are using it in a new way. 

If I were to design and sew a dress (not very likely), it would be

an original work, even though I did not weave the material myself.

The way I see, originality isn't so much using new material as it is using the material at hand in a new way, and adding a few personal touches.