> I'd be just as likely to say "I like black people, but <a notoriously criminal/amoral black guy> hurts the public image of black people and the cause of civil rights", sure.
Wow, I think you are hurting the cause that is your credibility.
Do you really think a member of a visible group acting badly doesn't hurt the overall image of that group? I agree individuals have every right to act as they please, but if you are the only e.g. Sikh in a Midwestern town, and no one there has ever met a Sikh, and you are a good person, people will generalize and believe Sikhs are good people. (This is why I as a white American in the Middle East would tip really well, be polite to everyone, help people who had broken down cars by the side of the road, etc.)
If you are a political activist campaigning for a cause (which drive through guy was), and you aren't aware that people will make generalizations based on your behavior, you will not be an effective campaigner. This is why e.g. Mormon missionaries dress well, are polite and friendly, etc.
If you are a member of a large group which is well represented in a population, you are less likely to be someone's only contact with that group, and thus generally less influential, but even then. This is why companies and organizations have policies about what members of that organization can do or say in uniform or when identifiable as a member, even when clearly off duty (so it couldn't be taken as an official statement).
There is something very important that you do not understand about people. I don't know why some people can't understand this easily. Maybe someday you'll have that moment when it clicks, and when you do, I think you may find yourself with lots of regret for your past ignorance. In the meantime maybe learn to see things from other people's perspectives instead of thinking what individuals who are different from you should act like.
Wow, I think you are hurting the cause that is your credibility.