Yes...some people downright despise what the NRA stands for, and they frankly hate that they have to keep saying "I believe in the Second Amendment"...because they really don't, and they're too chickenshit to say it. Wonder why that is?
Most Americans do support the Second Amendment, that's an absolute fact. Some would stress thinking more about the meaning of whole Amendment however, not just the second half that everyone quotes and the NRA has on it's lobby wall. They leave out the whole nasty "well-regulated" bit.
On the whole though, people support the right to own a gun in the US. What's more in dispute is the level of regulation. I'll show you another similar-looking chart, also from Gallup, here you go.
So right now today, the majority of polled Americans support the right to own a gun, but also think the regulations for a buying a gun should be more strict then they currently are. So apparently you can support the 2nd but still favor regulation after all, which is perfectly in line with what the Amendment says in the first place. They only people that don't get that are the people who want a gun free-for-all and those that want them completely abolished.