What is Maverick's "Harry Potter is about gangs" theory? How is the Harry Potter the same as a gang?

From the text:

“If it’s not that,” Momma says, “you’re giving your ‘Harry Potter is about gangs’ theory.”
“It is!” he says.
Okay, so it is a good theory. Daddy claims the Hogwarts houses are really gangs. They have their own colors, their own hideouts, and they are always riding for each other, like gangs. Harry, Ron, and Hermione never snitch on one another, just like gangbangers. Death Eaters even have matching tattoos. And look at Voldemort. They’re scared to say his name. Really, that “He Who Must Not Be Named” stuff is like giving him a street name. That’s some gangbanging shit right there.
“Y’all know that make a lot of sense,” Daddy says. “Just ’cause they was in England don’t mean they wasn’t gangbanging.” He looks at me. “So you down to hang out with your old man today or what?”