This was the Hogs' fault. You expect a second round opponent to give you some sort of competition. UNC's bench played 101 out of 200 minutes in their opening game, and I don't blame Williams for wanting to give the starters some game action prior to a tough regional next week.
They have four off days, so their legs will be fine. If anything, not playing them might have sent them into the Louisville (WSU, actually) game cold.
The down side is there is always a chance of injury, or getting punched in the face anyway.
There is no mercy in the tourney. However, I think it was stupid to leave the starters in and get them tired. There is also a good chance that running it up will frustrate the team they are playing and some bows might get throw Hanborrow (sp?) way next time, which could cramp their style.