Imagine that this was the last question of Mr. McCain's Q&A session. What impression would it leave in the minds of the audience?
The fact that only this segment, without the conclusion, appears on YouTube makes me wonder...
Q&A sessions are an important part of your speech. However, they wrest control from your hands and puts it squarely into the hands of your audience. You don't want that.
Always make sure that you leave a bit of time to conclude after you have answered questions. By doing so, you maintain control of your speech and you can end it on your terms, not on your audience's terms.