When you view that video, you have to remember the context. Herman Cain has to appeal to the base that will get him the nomination in the primaries, but also not make it impossible for him to move toward a position that can win the nation. It's harder to tell a candidate's final position because the composition of the primaries are so out of touch with the rest of the nation in the general election.
I always figured that a politician who will lie to you during the campaign is just plain dishonest and should be removed from consideration as soon as possible. If they lie to you when they need your vote, what stops them from doing much worse once they DON'T need your vote?
Innate dishonesty is one of the most prevalent and important disqualifiers for virtually any job. POTUS, cop, salesman, dog catcher, teacher... if they lie, they should be fired. If you catch them lying before they're hired... they shouldn't get the job.
WRT the Second Amendment, Cain is ignorant of the Constitution, is an idiot, or is a liar. Maybe all three. (IMO, PROBABLY all three.)
For those who don't understand the operation of the Bill of Rights, they were a condition precedent to the enactment of the Constitution. The anti-federalists (Jefferson, et al) refused to sign without a BoR. As ratified, all the states agreed that they were part of the Supreme Law of the Land. The Supremes have gone through a sort of legal square dance over the issue of "incorporation" of the rights spelled out in the BoR (never said the Supremes were all that bright - and often their stupidity is overwhelming... see Wickard v. Filburn on the Commerce Clause) but they finally figured out that the Second Amendment applies to the States in the Heller decision.
Sort of.
That said, under any theory of law, the Second Amendment is the Supreme Law of the Land. So in an honest Supreme Court, that would be the end of the story in every Federal, State, County and Municipal jurisdiction within the USA. But the Supreme Court isn't completely honest, so the legal masturbation will go on for decades as the "boobs in Black" come up with different ways to carve out exceptions, and appear to do the right thing, while doing the political thing.
An example of what I mean: In Heller, there is an exception to the "right to bear arms" that applies to "dangerous and unusual" arms. The thrust of the opinion is that machine guns fall into this category because they're both "dangerous" and "unusual".
Of course, a firearm that isn't "dangerous" is pretty useless as a firearm. (Might still be fine for a mantle piece.) Even BB guns are "dangerous". Surely handguns, shotguns and rifles are "dangerous". So "dangerous" is just a term the BiB threw out as a gratuitous qualifier intended to help build the case for the second part of the exception: "Unusual". Like an AK-47 or an M-16.
Except, the reason that these full-auto firearms are "unusual" is because of the NFa 1934 and the GCA 1968, which effectively banned ownership of any new machine guns. Get it? The exception eats its own tail. If not for the unconstitutional taxes/prohibition in the NFA/GCA, machine guns would likely be as plentiful as AR-15s and AKS are today. But the GCA made them "unusual" and so subject to special limitations.
Of course, there's nothing in the Second Amendment that says, "... the right of the People to keep and bear arms, so long as they aren't dangerous and unusual, shall not be infringed" - but that's the way the Boob-in-Black created that particular canard, that judicial LIE.
Now suppose the ruling had been on the constitutionality of the 14th or 19th Amendments. The BiB version might have read, "No one shall be compelled to be a slave... unless they're already a slave, in which case, this doesn't apply", or "All women may now vote - unless they've never voted before, in which case they may not vote now."
Except in the case of Heller, the key word is "unusual", as applied to firearms that are only "unusual" because the government made them "unusual".