The founding fathers of The United States were aware that corrupt
governments could forbid the use of individual firearms in order to
manipulate, control, and persecute citizens. After battling with the
British, it was clear to many Americans that the ability to bear
personal firearms was necessary; nobody wanted another government
(including the newly forming U.S. government) threatening them,
without a way to defend themselves. This is how "the right to bear
arms" found it's way into the Bill of Rights.
Given that Americans, as a general rule, view the Constitution and the
Bill of Rights as nearly sacred documents, it's not surprising that
"the right to bear arms," while controversial, has not been removed
from our list of rights.
For more information, check out "The Right To Bear Arms: A Phenomenon
of Constitutional History," at Catholic University of America Law
Review: http://www.saf.org/LawReviews/Rohner.htm , which includes the
history of limitations to the right. Also check out "What Does the
Right to Bear Arms Mean?" from The Straight Dope:
http://www.straightdope.com/classics/a5_123.html , which covers the
controversial topic of interpreting the right.
"right to bear arms" historically