I'm not sure what advice they could have given him. To someone with common sense, a Civil War rifle doesn't look like a threat, it looks like an antique, especially if it's just being carried like one.
If you put a sleeve on it, nobody can see what kind of rifle it is, and someone in today's panic-first mode might assume it's a modern one that could be a threat on a campus.
If you put it in a case, (good luck finding one that long, if it was an infantry rifle and not a carbine!), likewise.
When I was at the University of Miami in the 90's, the ROTC drill team members walked to and from practice with their M1903 Springfields and kept them in their room, and nobody fussed or called the police. What year did anything that vaguely resembles an antique firearm become reason to panic?