I think of this and it just has to be whoever is most harmless. The least threatening program to my school or to any school with a big fanbase.
In the past 50 years, who is the worst program? First, let's remove the private scholarlies:
.336 Vanderbilt
.366 Duke
.386 Northwestern
.405 Wake Forest
Okay, with those out of the way, here are the worst public, P5 programs. I think our "winner" will be the one who lacks a rival (Rutgers?) or who's rival doesn't return the favor.
.355 Oregon State
.383 Kansas
.386 Indiana
.412 Iowa State
.425 Illinois (wow, that's shameful)
Okay, so if their rival is really good, then it has bigger fish to fry, and the rivalry is one-sided in terms of passion. If the rival is bad, then it's more contested and matters more to both sides.
Oregon State having the worst winning % and having a strong rival (Oregon), makes me lean towards them. Duke's rival isn't as good (UNC), both both care more about basketball anyway, so it's sort of a big shrug. Kansas' top rival is Missouri? or K-State, both of which are decent long-range programs, but neither is as good as Oregon, and so neither is as apathetic towards them.
I'm going Oregon State. They even have a harmless mascot.