Graves has helped the Bulldogs produce an 18-2 record and a 7-2 mark in the Horizon League, but he made only two of 11 field goal attempts Thursday and scored five points.
Campbell and Howard both had 15 and Mike Green added 13 in what was Butler's 10th win in 11 games.
Loyola-Chicago (6-13, 2-7) was led by J.R. Blount with 16 points and Andy Polka with 13.
Butler went on a 15-2 run midway through the first half, then fought off a Ramblers comeback to take a 32-23 advantage at the break.
The Bulldogs put together a 12-4 surge early in the second half and their lead was at least seven points the rest of the way.