I see that this video of Obama engaging a voter on terrorism and immigration is getting some play around the web. The title of the YouTube clip--"Obama yells at elderly Iowa voter"--tells you all you need to know about the context in which it's been circulating. (According to this site, Drudge linked to it earlier today, though I can't find it now.) Having attended the event in question yesterday, I can tell you that the video has been framed and edited in such a way as to misrepresent what actually happened. The woman in question was a Republican named Jane Svoboda, who asked her questions in a pretty sharp and mean-spirited way. Obama began to answer them in a perfectly calm tone. The woman proceeded to interrupt and hector him several times over the course of the response. Each time she did, he would grow more animated--not nasty by any stretch, just the way someone gets when they care quite a bit about an issue. It's true that at times he almost had to yell, but that was only to make himself heard above the cheering of the crowd, which was very much sympathetic to what he was saying and unsympathetic to the woman, who'd outed herself as a bit of a bully.
All of which is to say, "Obama yells at elderly Iowa voter" is almost completely backward as a description of what happened.