You don't win over allies when you yell at people who have good intentions,
Let's get a few things out of the way first...
1. Ben Carson isn't actually running for president. I think it would be premature for him to do so.
2. The 2nd Amendment is non-negotiable.
... but Carson isn't some Republican official who is preparing to sell out the country. He's a successful doctor who is taking on a role as a conservative commentator, but he comes from a background of having lived in dangerous cities like Detroit and Baltimore.
Instead of rushing to attack him, it might be better to understand where he's coming from and educate him.
The "damning" quote that is being circulated shows his confusion about the issue and his attempt to come to grips with it.
"When asked by Glenn Beck if people should be allowed to own semi-automatic weapons, Dr. Benjamin Carson said: "It depends on where you live. I think if you live in the midst of a lot of people, and I’m afraid that that semi-automatic weapon is going to fall into the hands of a crazy person, I would rather you not have it." (Glenn Beck Show, March 1, 2013)
Carson's comments reflect his life experience. He respects the Bill of Rights, but he has trouble applying it to the everyday reality of a major city where shootings are commonplace. It's a problem that a lot of urban residents have.
A lot of city dwellers look up from a front page story about three people dead in a gang shooting and have trouble believing that the answer is less gun laws. That doesn't mean they're right, but it does mean that they need to be educated. Most of the country still supports the 2nd Amendment, but support is notoriously weak in many cities.
African-Americans tend to support gun control in large numbers. This is an emotional attitude that comes from life experience. It has to be overcome with facts, but it's hard to convince people who have lived a certain way that their life experience isn't valid.
Both of these are reasons to reach out to Carson. He doesn't appear to have his mind firmly made up and is still grappling with the issue. If he actually enters the race or becomes a vocal advocate for gun control, it might be another story, but at this point it would be better to show him why gun control doesn't work instead of denouncing him loudly for not taking the right position on an issue that he is clearly still uncertain about.
You don't win over allies when you yell at people who have good intentions, but aren't fully on board. There's a big difference between someone like Carson and Crist.
Urging Carson to run for president is premature. Treating him as if he's already in the race is also premature.
Carson understands the moral and legal principles, but he's hazier on the social functions. It's a challenge, but it's the kind of challenge we need to meet if we're going to win the war of ideas.