The Guardian provides fuller context with an extended clip and notes that this comment from Paul was a follow-up to his belief that the U.S. could have (and should have if possible) captured Osama bin Laden rather than assassinate him.
Ron Paul was also booed when he attempted to explain why the US did not need secretly to enter Pakistan to kill Osama bin Laden. Paul pointed out that the US had managed to capture Saddam Hussein alive, and that the Iraqi government had put him on trial. The line did not go down well with the audience or his Republican rivals.and
Here's the transcript of Ron Paul's comments, after being asked about his opposition to the US assassination of Osama bin Laden:Given the probability that many of those Republican voters who booed identify themselves as Christians, one might wonder if they experience any cognitive dissonance at booing what is supposed to be one of their bedrock moral precepts.There is proper procedures rather than digging bigger holes for ourselves. That's what we have been doing in the Middle East, digging bigger and bigger holes for ourselves and it's so hard for us to get out of that mess. And we have a long ways to go. We are still in Iraq and that's getting worse and we are not leaving Afghanistan and the American people are sick and tired of it, 80% of the American people want us out of there. I am just suggesting that we work within the rule of law. Like only going to war when you declare the law.