Some of the Founders Were Slave Holders
Some people argue since the founders had slaves, and times and values have changed, the Second Amendment no longer applies.
Granted this is a seriously malformed argument, but there are people who earnestly posit such a statement. Of course we could preface the beginning of any statement accordingly in an attempt to disregard any of the rights in the Constitution.
Like it or not the Second Amendment is law. The law cannot be ignored because one considers the practices of lawmakers at the time disagreeable or immoral by today's standards. By the same reasoning, if our President or members of Congress commit immoral acts, is the legislation they passed suddenly invalid?
Incidentally slavery and the slave trade were abhorrent to many of the delegates at the Constitutional Convention, even to some from the South. However Southern votes were necessary for ratification, thus slavery was protected in the states where it existed.
Whatever the vices and imperfections of the Founders, they were masters at establishing a republican form of government. This is not saying the government they established was perfect. They gave us mechanisms for changing the laws and Constitution as necessary.
Another slavery claim, arising from a law review article by Carl T. Bogus, in 1998, asserted that the Second Amendment was ratified to preserve slavery. Here is a rebuttal: http://lawreview.byu.edu/archives/1998/4/kop.pdf (starting from p. 1522).
Unrelated to slavery there are additional misleading claims in that law journal article. One example, after reading "III. THE MYTH OF AN INSURRECTIONIST RIGHT" from the Bogus article, compare it to the first section here: http://www.guncite.com/gc2ndcont.html.
Some of the author's previous affiliations:
VIOLENCE POLICY CENTER, Washington, DC National Advisory Panel, 1993-Present.
HANDGUN CONTROL, INC., Washington, DC Board of Gov., 1992-93, Board of Directors, 1987-89.
THE CENTER TO PREVENT HANDGUN VIOLENCE, Washington, DC Board of Directors, 1989-92.
A website ironically called "truth-out," referring at length to the Bogus article, http://truth-out.org/news/item/13890-the-second-amendment-was-ratified-to-preserve-slavery, fails to mention his affiliations. On the other hand, a law journal article penned by a former or current NRA board member would most likely be noted.