Joan, I agree with you that Obama should be commended for admitting that mistakes were made and that he needs to seek out reasonable solutions to the problems with security. But as you likewise suggested, he also needs to stop caving into the Republicans in regards to using brutally totalitarian methods in the never-ending "war on terror" that go against American values and the Constitution. Also, I wish Obama would stop pandering to the Republicans by declaring, "we are at war!" Terrorism is not bound to any one nation, and it shouldn't be treated as a military problem but as a law enforcement issue, and the U.S. should consider its foreign policies that provoke terrorist attacks on the U.S. which serve to discourage other "free" nations from working with us to solve the problem.
As for the commenters on your letters page who tell you to stop putting down the "evil" Republicans...considering the policies they continue to support regardless of how many problems these policies cause both at home (with regards to severe erosions of our civil liberties that all Americans are supposed to hold dear) and abroad (with regards to the imperialist policies that cause anti-American terrorists and sentiments to grow faster than we can stop them), they deserve to be criticized every chance you get. The comparison you made between Obama's reaction to the pants bomber and Bush's reaction to the shoe bomber was quite apt. Don't cave into their demands to "lay off" of their beloved party and give them a free pass like the Democrats usually do.
That being said, I agree with the request from the same commenter to cease pandering to Democrats for the least little thing they do right and expect nothing less than a near-total repudiation of all their support for unconstitutional measures, including pre-emptive wars, detention without due process, support of the Patriot Act, illegal wire-tapping of American citizens, etc.