Yes, publishers and middlemen have all kinds of rationalizations for trying to kill e-books, but calling any of them "legitimate" is shilling so hard you could pence a crown.
All the arguments based on classical economic theory only work if the assumptions of classical economics hold, particularly the assumption that there is a free market.
Amazon is arguing for its freedom to set prices it charges in its ebook store; that would be no concern of the publishers if we lived in a world where ebook users could simply buy books in non-proprietary formats from any Internet storefront they wanted. But we don't live in such a world. We live in a world where most ebook readers are controlled by Amazon and inextricably linked to its store. It wouldn't have been hard for Amazon to build the Kindle that way. Define some public book trading protocols, bootstrap the standard by building those protocols into the Kindle and Amazon's online store, and instantly the world is a better place for everyone except printers and bricks-and-mortar bookstores with no Internet presence. But Amazon didn't do that, because the Kindle is designed to tie the user to Amazon, the way the iPad is designed to tie the user to Apple.
So what we're looking at is a maneuver by Amazon to corner the market on books *in general* by killing off the traditional paper book trade. Preserving the ability to buy most books from someone other than Amazon seems like a legitimate reason to me.