"When I saw in the paper that they were No. 1 and we were No. 3, that hurt my heart," Graves said. "We took that as disrespect."
Senior swingman Bryan Nolan scored 11 in a key reserve role for Atlantic City (7-2).
Sophomore guard Leon Daniels scored 13, and senior forward Junior Saintel added 12 for Holy Spirit (9-2).
"We did a brutal job executing offensively," Holy Spirit coach Jamie Gillespie said. "We'll learn from this. There's no such thing as a must-win game in January."
The victory was Atlantic City's 37th in a row over South Jersey opponents. The Vikings' last loss to a local team was to Paul VI in overtime on Feb. 12, 2012.
Atlantic City's big-game experience seemed to show in the second half as Graves and White, veterans of teams that won the last two Group 4 state titles, seized command of the game.
Graves, a 6-foot-1 guard, slashed through Holy Spirit's defense for layups, drew several fouls, and found open teammates for layups.
"He's such a dominant player that at times you let him go," Atlantic City coach Gene Allen said.
Allen said the key to the game was Atlantic City's ability to stay close with Graves and White, a 6-6 forward, on the bench with two fouls in the second quarter.
"I took that from John Chaney and Clarence Turner: Two fouls and you sit," Allen said.
Long known as a fast-paced team, Atlantic City has developed into a stingy defensive squad that flourishes in tight games, executing well in half-court sets.
The Vikings were far and away the more patient team, spreading the floor and running their offense in deliberate fashion.
"We wanted to control the tempo," Graves said.
Holy Spirit led by 33-29 midway through the third quarter, but Graves sparked a 16-3 run that turned the game.
"We were sitting there, and the younger guys did a great job," Graves said of himself and White in the second quarter. "When we got in there, we were like: 'It's our time. We're going to put this away.' "
Atlantic City 11 12 18 21 – 62
Holy Spirit 14 11 11 10 – 46
AC: Isiah Graves 13, Dennis White 16, Kevin Allen 6, Jamir Prevard 7, Tashad Reynolds 4, Lamar Thomas 4, Bryan Nolan 11, Najee Wimbish 1.
HS: Junior Saintel 12, John Middleton 6, Uuhmad Collier 7, Leon Daniels 13, Jordan Taylor 6, Matt Sommers 2.