Its a joke. The stereotype that black people love fried chicken added to the fact that Atlanta has a lot of black people means that he is saying the black people are going to attack the truck. Haha
He was making a joke because Atlanta has a very high African American population. African Americans have a stereotype attached to them that they love Chicken (particularly KFC), Koolaid, and waffles.
your friend is making a joke suggesting that they would attack the truck driver to get the chicken.