Dick Cheney's response to Obama's civil liberties speech in May 2009 was notable for putting forth the same claim, that the Bush administration prevented any terrorist attacks after 9/11, also failing to mention the anthrax attacks, which probably did more to frighten people than the 9/11 attacks.
Some people would like the fact that a number of people were killed and congressional mail service disrupted for months by someone who has yet to be unidentified and who the FBI concluded used biological weapons from a US government research facility to disappear down the memory hole. The house judiciary committee, which oversees the justice dept. and thus the FBI, was highly skeptical of the FBI's claim that Bruce Ivins was the sole individual responsible. Check Grassley, a Republican, was openly skeptical that Ivins was even involved. (Ivins did work at a biological weapons lab, but he didn't have access to the strain that was used in the attacks.)
Remember, facts are now judged not only by their truth and relevance, but also by their political significance.