Why do many retail books stores refuse to carry titles published by CreateSpace?

In the never-ending battle between Amazon and the rest of the book-selling world, the fight has spilled over to small, mom-and-pop bookstores. These stores, as well as larger chains of books stores, have begun to refuse to carry any books that are published or distributed by CreateSpace. Why is that? Simple- because CreateSpace is owned by Amazon, and many blame Amazon for putting the smaller brick-and-mortar bookstores out of business. In an attempt to protest that wrong, many book stores flat-out refuse to carry any book published by CreateSpace. Many unsuspecting authors do not even realize this until it is too late. In the giant battle between Amazon, Apple, Barnes & Noble etc., it is best for an author not to align with any one particular side, but instead to get his/her book published by a publisher who has the ability to distribute books through all vendors- both digital and print versions. Check out Page Publishing for example- they are one of many such publishing companies.