If we think of ebooks as property, then once that ebook comes into our possession we are able to do with that property what we will, short of using that property to cause harm to another perhaps.
It might be said that circumventing DRM does cause an economic harm to the distributor of the ebook, but there is no proof to this. I will say that circumventing DRM and freely sharing ebooks causes a long term economic gain to the distributor of the ebook, especially so if the ebook came with a mechanism for payment that was retained within the book through the free transfer.
Abolishing copyright will not cause the sudden loss of thousands of jobs, but it might create them.
