The case for mistrusting Muslims

In my many adventures, I once met a very Westernized Pakistani woman who told me never to trust Arabs. I never asked her if she still practiced Islam, but she was very adamant in saying that Arabs are the most untrustworthy people on earth and she sounded very convincing. It made me wondered that, if knowing that a certain ideology or religion came from such a breed of devious people, one would still count himself/herself with such.