Even if the one guy was getting shafted, I don't like the veto. There's no reason to veto someone for being stupid. Honestly, everyone should worry about their own teams, and vetoes should be reserved for collusion or firesales in non keeper leagues. It's not the league's job to decide what trades are okay since everyone in the league holds a bias. (Whether purposefully/consciously or not)
As far as trade value goes, I've seen worse that didn't get veto'd...
Anyway, I don't like the veto and that's my two cents.