I have a funny story about this...
One day, I was visiting with my friend at her apartment and her roommate was party to the conversation. When it came up that I was Greek, she talked down to me with disdain and made comments like "I would never pay for my friends" and "I don't really like Greeks" etc.
I simply let them pass without argument, cause really, with these people it's simply not worth it. Their prejudices probably aren't going anywhere.
A couple weeks later, it was Greek Week on our campus. My fraternity, well known on campus for hosting our cookouts in the quad, was serving up a huge amount of food that day - burgers, hot dogs, chips, soda, etc. Well who do I see come up to the grill but that same girl!

I commented to her nicely that "I thought you didn't like Greeks!" and her response was "I don't, I just like the free food."
With that, I turned to my brother Garth who was manning the grill...and I said "Garth, you know, I'm sure glad I paid for you to be my friend" and his response said it all...
He said
"I'm glad you did too Matt, because magically, these burgers appeared on my doorstep this morning." The look on her face was priceless