The majority of liberals share certain tendencies. So do the majority of conservatives.
But in the case of liberals, some of their tendencies are so divorced from reality that they actually resemble a mental defect. Chief among those is the way that whenever a terrorist event takes place in this country, liberals reflexively assume the perpetrator is some stupid probably-Christian white guy from middle America -- but never seem to consider that he might be associated with Islam, even though most terrorist acts over the last four decades have been committed in the name of Islam.
After the attempted bombing in Times Square a few days ago, liberals started profiling. They explained who they thought the bomber would prove to be, and the image they saw was of the same guy they envision whenever they speculate about people who support the Constitution and dislike intrusive government. New York's own mayor (ignoring that his city had already been bombed by Muslims on 9/11 and in 1993) opined that the Times Square bomber was likely "homegrown, maybe a mentally deranged person or somebody with a political agenda that doesn't like the health care bill or something." But now somebody has confessed to being the bomber, and it turns out he is a Muslim born in Pakistan.
This blame-our-own-first mentality might be less irritating if the left could point to a series of examples in which white American Christians have engaged in indiscriminate acts of terror, but they can not do that. Even Timothy McVeigh, the one name they think they have in their quiver, does not fit the bill because he described himself as "agnostic." For good measure, he also said "science is my religion." (Hmmm, his words were right in line with the way metropolitan Democrats always talk.)
Complaining about this particular liberal tendency is so easy it feels like cheating, but it is still important. The tendency encourages people to not be on the lookout for danger in places where it clearly exists, and to instead look out for it in places where it is an anomaly. Not complaining about the tendency would cause it to become even more prevalent, and that would make us less safe every day.