Why is some movies,books,and music banned in America when there is a right to free speech?

I was on Amazon and there was some books and I came across this list. 451 banned in Mississippi,The Irish Fairy Tale Book: Myth and Romance from the Old World , The Breakdown of the Criminal Justice System in Canada by former B.C. Judge Les Bewley, The Evil Empire: Globalization's Darker Side by former Liberal cabinet minister Paul Hellyer,Stalking the Wild Taboo by Prof. Garrett Hardin, an ecologist from the University of California at Santa Barbara .Now in the land of free speech and to be able to say or write what you want and sell it,How can the government by all rights ban anything.We have a right to share ideas,speech and even assemble if we want.

The movies are some what fewer with movies such as The Tin Drum and the Death movie series to my knowledge.Even though I have never seen these movies I find it disturbing that we have people in the government that says that something can't be seen here because it may offend a few people.

Is it not unconstitutional for them to tell us what we may or may not watch,read, or listen to?