Who would have known? I wouldn't. I don't believe for a second that the new guy on the job deliberately offered a gift to piss off his fellow firefighters...the people he would work with and possible die with at a fire.
The firefighters need to rally around the new guy and offer their support. Otherwise, they need to be fired too. All these fools did was reinforce a stereotype and show their 'thin' skins. The 'new guy' is now better off. He won't have to work with idiots and thin skinned racists.
The Watermelon originated somewhere in Africa. It's cultivation and use spread. People all over the world eat it.