They were responsible for 9/11, many terrorists come from Islamic countries, they perform attacks on people who criticize or stray from Islam, they brought it on themselves by not doing something about it.
I believe that most Americans do because our media is trying to make Muslims out to be terrorists. The media portrays Muslims as dark skinned people wearing very conservative (full coverage) clothes with bombs strapped on underneath.
There are many, like myself, who know that Muslims are not terrorists and Islam is actually a peaceful religion (except for Jihad and the killing of Infidels). I know many, many Muslims and they are fantastic people!