Rewriting the 2nd

The New American has compiled a interesting collection of entries from Common Core curriculum materials:

In a textbook approved by Common Core for use by students studying for the Advanced Placement (AP) history exam, the Second Amendment is defined this way: "The Second Amendment: The people have the right to keep and bear arms in a state militia." 

Another book that received the Common Core stamp of approval informs students that the Second Amendment “grant[s] citizens the right to bear arms as members of a militia of citizen-soldiers.” 

Then, there is a worksheet reportedly approved by Common Core for use by history teachers in preparing lessons on the Bill of Rights that “informs” students, “The Government of the United States is currently revisiting The Bill of Rights. They have determined that it is outdated and may not remain in its current form any longer.” 

Actually, the statement is not a statement of fact, but an introduction to a proposed lesson asking the students to “prioritize, revise, prune two and add two amendments to The Bill of Rights.” 

Finally, there is the description of the Second Amendment published in a book approved by Common Core for use in elementary schools. 

Regarding the Second Amendment, the authors of the book state: 

This amendment states that people have the right to certain weapons, providing that they register them and they have not been in prison. The founding fathers included this amendment to prevent the United States from acting like the British who had tried to take weapons away from the colonists.

How can subsequent generations of Americans defend the Second Amendment (or the Bill of Rights, for that matter), if they don't understand it, and are deliberately misled as to the meaning?