How do I deal with some really rude people?

I work retail (enough said huh?) I work in a drug store. With the economy the way it is, its all I can find at the moment. I am nice and polite to all customers. When I started working there in February I never saw color, race, nationality or age. To me, every person was simply just another person. Sure some were more friendly than others. Some people had a bad day and would take it out on me. Now a few months later, I am seeing things a bit differently. I hate to say this but foreigners are the most rudest of all people and I don't understand why. Is it the way they were brought up? Do they simply hate americans and if so, why did they move here to our country? By moving here did they not want to take the initiative to even learn to speak our language so that they could communicate with others? I have found the most spend thrift people of all races, colors and nationalities are men. White american women spend more on what I call useless items. Some women come through my line spending 100's of dollars on face creams, makeup and "as seen on TV" items. The most nicest people who come through the line are the elderly who are retired and well into their 80's and at least take the time to mutter hello back to me. Now of all people, of all races, nationalities, etc. The most rude thing someone can do at at register is talk on your cell phone. Why is that phone call so important? Is time so scarce that a person cannot either finish the conversation prior to getting to the register only to hold up the line because they lack the ability to multitask as good as they thing they can? Is it because they dint care about other peoples time and how much time they themselves take at the register TRYING to multi task..... only to have a question for me.. but wait until the conversation is over before asking? I could go on for quite awhile.. but you get the picture. What can I do to overcome these obstacles while trying my best to service all customers at minimum wage? I try not to take these things personally because i know its not intended personally. I know the customer is always right and I am always wrong in this scenario but anyone have any suggestions? Sorry I just needed to vent.