The typical American perception of Islam and of Muslims has never been particularly enlightened. The mainstream has never really accepted "the other" in our society, preferring to view the United States as a "Christian nation" while, at best, ignoring the presence of other religions as well as the non-religious. While the images of Muslims post-9/11 became worse, Arabs and other Muslims have long been referred to by derogatory names such as "towel-head", "camel jockey" and "sand nigger" long before the 2001 attacks.
With some religions which have violent adherents, a case can be made at least for some, like Christianity and Buddhism, that the founders were peaceful men, and that it is only their followers who used violence to advance their cause. This is called the "No True Scotsman" fallacy. It refers back to a apocryphal story about someone accusing a Scotsman of some crime. The accuser is then told that it couldn't be, because Scotsmen don't do that sort of thing. The accuser responds that, yes, the perpetrator was a Scotsman whereby he is told that no true Scotsman would be guilty of such. We see this all the time when Christians do un-Christian things and other Christians rationalize it by stating that they aren't really Christians. Sure, it's a logical fallacy, but the fact that the founder of Christianity was peaceful makes it at least plausible.
The same cannot be said for Islam. Their founder, Muhammad, if he existed as described in the Koran, was manifestly a man who spread his new religion by the sword and his successors did the same. There are numerous sections of the Koran that advocate violence: killing of "unbelievers", killing of apostates, killing of conquered people who resist. There do appear to be sections that advocate living in peace with "the people of the book", i.e. Christians and Jews, but others that advocate their eradication. It appears that the Koran defines "peace" as "The Muslims are in charge and everyone else are second-class citizens (if that)". "Peace" is submission to Allah - "Islam" means submission.
There are certainly many Muslims who are not violent, do not support violence in the name of their religion and sincerely believe that Islam is a religion of peace. It seems to me that, similar to many Christians who cherry-pick their beliefs in order to deny the more unsavory parts of the bible, these "peaceful" Muslims mentally edit out the parts of the Koran that they disagree with or find morally repugnant. I do not believe that all Muslims are extremists, or are potential terrorists, but the book upon which they supposedly based their lives is a book of violence.
