I live in the Midwest. Even though I work in a city of around 400,000 people, and live in a metropolitan area around a million, I see friendliness all of the time. This comes from people of many nationalities and races. Sometimes, even when people don't seem friendly at first, they respond well to friendliness.

People will give you a wave or nod and a smile, they say thank you when you hold a door, or hold a door when you need it.
Not all Muslims are Arab. Not all Arabs are Muslim. Did the store owners announce their religion? Do you know whether, if they were Muslims, they were practicing Muslims? Do you know whether it was their religion that made them unfriendly? Maybe it was a lack of faith that had soured their feelings. Maybe a language barrier made them uncomfortable.
In any event I don't see the logic of drawing conclusions about all Muslim practitioners on the basis of an attitude by a couple of store clerks. Similarly, one can't draw conclusions about all Muslims on the basis of acts of terrorism by a radical group within the Muslim Faith.
There were terrorists in Ireland, but that doesn't translate to all Irishmen. Long ago, the Catholics engaged in murderous crusades, but that doesn't mean that Catholicism is a murderous faith. Just 150 years ago, Americans owned slaves. Jim Jones, who professed to be a Christian, participated in a mass suicide/murder. Different nationalities within Africa have murdered others because of tribal hatred. A Slavic dictator murdered thousands in "ethnic cleansing." The blame for those sins and crimes does not belong to the races or religions or ethnic groups who perpetrated them. They belong to the sick and deranged among those groups who found various ways to manipulate hatred and ignorance.
Unfortunately there are those within this country that want to promote hatred. Too many people accept such vile messages because they don't know the truth, and, thus they are susceptible to the misinformation that promotes the message of hate. Shame on people like Gingrich, the Jewish Defense League, and O'Reilly, who know better, but for one reason or another, find it to their advantage to find ways to divide people. (I didn't include Palin and Beck, because I'm not sure they have the intelligence to know better

) I believe America is better than that.
Regards,
D-Ray