Suspicions, sure. But it is bad for business for them to involve their bookstores in a political campaign. They make money from selling books on both sides of the aisle, not to mention the simple fact that "conservatives" probably tend to buy more books, music, and magazines, so why risk alienating at least half of their customer base?
Those CEOs would be booted so fast if they involved their politics in their business. Or rather, they'd be booted if they were caught.
So the question is if there is a memo stating that liberal, bush bashing books be given prominence over conservative, Kerry bashing books. If so, that memo should be outed to the board of directors and the shareholders.