H.S. textbooks misstate Second Amendment rights

High School textbooks in at least two states (S.C. and TX), misstate the Supreme Court- approved Second Amendment rule. The  books state that the Amendment only protects the rights of those who are members of the militia.  This is contrary to what the U.S. Supreme Court ruled in D.C. v. Heller and McDonald v. Chicago.  Is this incompetence or is it ideologically motivated?  I still see lots of posts and letters from people who have probably never read either decision, limiting the right to militia members.  Ignorance is bliss for some. Our Bill of Rights is arguable the most important legal document in the land.  It's easy to defeat rights if people don't know they exist.  If you don't like the current interpretation of the Second Amendment, don't lie about it, propose an amendment.