If that's the case, then Demarcus Ware who was the 11th pick overall from Troy State University - (smaller than Southern U) shouldn't have been drafted either.
The Texans took a player from Hampton in the 4th round, a guy from ULaLa in the 6th, and a player from Grambling in the the 7th.
The Packers took a player from Bethune Cookman in the 2nd round
The Patriots drafted a guy from Toledo and one from William Penn.
There were guys drafted from Akron, Albany, Bowling Green, Grand Valley State, Louisiana Monroe, Murray State, Marshall, Saginaw Valley State, and Tuskegee.
The point is there are a lot of players from small schools who get drafted every year. Some in very high rounds.
Playing in a small school - small conference might handicap a player a bit from a visibility and competition standpoint, but I'd venture a guess that's not the only reason this guy wasn't drafted. There are a lot of undrafted free agents that make it in the NFL but if you're good enough to be drafted, typically the scouts will find you in most cases. Obviously the Texans knew about this guy but didn't think he was draft-worthy. Some guys just need time to develop more than others and that might be the case with this guy. He looks more like a guard than a tackle to me. I wish him and all the other undrafted FAs all the best. For most, it will be their last opportunity to play competitive football.