How much do you know about Pakistan, its Army and safeguarding anyone for that matter? You forgot, President Busch had played "cricket" in Islamabad with kids, when the WOT was in full swing.
I know parts of Pakistan are troubled but your post makes it sounds like the POTUS may be going in jungles around the Amazon totally unsecured. Also, if you pay attention to terrorism or even the US forces experience in Iraq and Afghanistan, its very difficult to protect yourself from the terrorists in Civilian disguise, as its not an open war. Similarly, do you expect the Pakistani military or anyone to kill everyone passing by its bases? NO. And if a few of these passing by civilians are terrorists in hiding, how do you protect yourself from that attack? You can't. No one can. Until the entire terrorism base is cleansed out, destroyed and these terrorist bastard*s killed.
Do remember, how we look at Pakistan due to many current and historical reasons may be different than how they've dealt with terrorism. They've lost over 40,000 soldiers and civilians in this war. In the beginning, they were fighting with us, no matter how many questions and suspicions we may have, that is the reality and a factor the US government always considers. Now, they are fighting to clean up their country from this cancer of terrorism and the entire globe supports them.
BTW, the POTUS's security is a responsibility of the very capable United States Secret Service. Not a Joe Shmoe on the street. The USSS doesn't allow any foreign body to create, implement or secure OUR Presidents security. The SS guys do it and they've been doing it for centuries. Our presidents have been to actual war zones and back. I don't think going to Islamabad is uncontrollable risk. The risk is a little bit more than what any POTUS would face in India, China or other foreign countries. We are not liked by a major part of the world due to our freedom, open society and our economy's power, just to remind you of it.