I think the hog was a metaphor for Hispanics taking over, stealing from black culture and replacing white people, similar to the architect's "human beings are a virus" metaphor in The Matrix Reloaded.
The good ol boy shopkeeper, Clyde, is all exasperated like "oh, boy, this is bad. You got feral hogs." And getting rid of em ain't as simple as using hog repellent. "You can thank the explorer, Hernando de Soto for this bullshyt." Hernando is a Spanish explorer who brought these razorbacks to the US. They're his descendants; Hispanics are the descendants of Spanish explorers / conquistadors.
According to Clyde, the "dirty hog" is coming for whatever Alfred is growing. Alfred gotta take that fukker down. Al just wants to poison it in the humane way. He doesn't wanna clap it with a headshot with a gun and be another stereotype. He's cool with the hogs. They've never bothered him. He doesn't see them as a threat to his artistry and way of life.
Clyde tries to impress upon him how serious these dirty Spanish hogs are. He knows what they're capable of. They killed a lady in Texas. They're down there near the border infringing on his people. According to him, "these things ain't no bedtime story animals. They don't deserve no sympathy. They are aggressive. They are invasive. They will not stop until they destroy everything you have. You got to kill them before they kill you."
Al can't believe it. He just laughs thinking the hog ain't gonna kill him. He's incredulous. He doesn't consider the seriousness of the issue and overlooks the hog and it's what is has planned for him. Clyde, the white man, knows the Spanish hogs, courtesy of Hernando de Soto, will do to Alfred, the black man, and his people, what they're in the process of doing to his people.
The whole point of the farm is to have options. Atlanta ain't going nowhere. Donald, who has a farm, got options now with his Amazon deal. Atlanta, the show, despite ending, gonna always be there for us to go back to.