Because many believe they are supposed to kill all infidels. In other words they have no tolerance for people worshiping God in a way that is different from way that they do. The radical ones have no tolerance for Christians or Jews. I believe in Jesus as my Savior. They see Him as a Prophet and nothing more. They want to kill me for not following their religion that I don't believe in. I don't believe that women are lesser people or that they must cover their heads. . I go out of my way to be friendly and speak to the Muslim women I meet shopping. I am a friendly person, and I want to let them know that I am not down on them, that I am a woman too. If I like what any lady is wearing, if it is a pretty fabric, I tell her. One lady's little boy was very cute, so I told her so. We talked about prices & things. It was nice visiting with her. . I wonder if she is looked down on because of what the terrorist did. I hope that other non-Muslim women are friendly and reach out to other women.
Terrorists are usually thought to be from the Muslim community. Many terrorists have been Muslims, or have said their act was committed because Allah told them to. It's very racist, because most Muslims are, in fact, NOT terrorists.
Some Muslims are terrorists. So are some Christians, etc. But because the people responsible for 9/11 were Muslim and (I think) believed that they would be rewarded by Allah after their deaths for their actions it has become a common, if misguided, belief that Muslim = Terrorist.
Because they are, as stated above, ignorant. Terrorists seem to come in all colors, races and religions. Muslims are just in the news at the moment. Some forget about Neo-Nazis, RIRA, Communist Party of the Philippines, LTTE or even the good old white Christian folk who murder doctors in church or bomb women's clinics. The Muslims aren't special by any means.
I travel the world and have met people of many religions. I have never met a Muslim that was not nice to me. Often they seemed to go out of their way to help a foreigner, smiling as they did. When my husband passed away, the ambulance and the fire truck came during the night. The Muslim lady who lived across and three houses up the street was the first of my neighbors to come see if she could help. We had never spoken to each other before. We had smiled and waved at each other when we drove past each others' houses or seen the other outside. But she was the first one there. I will never forget that.