Many African Americans and others celebrate Juneteenth, which commemorates the end of slavery in the United States. If I were black, I would be offended by the 'fried chicken' display.
Did the people holding the party see/know about the display and that a black person was invited? We know that there's no law against being a bigot or having poor taste but that doesn't mean the offended must act like they are not offended.
If the offense is worthy of a law suit is another story but let's not pretend that their was no offense.
The offense was turning “juneteenth” into a national holiday.