Pro Leagues - Lock consolation bracket teams
They shouldn't even exist, just like in the sports they follow. My one hockey league had the 11th place team add the top 3 FAs this morning to his team that has nothing to play for.
If you want people to take the Pro Leagues seriously, stop letting teams that aren't competing for money anymore take the top players remaining on the FA/Waiver wire.
Or institute FAAB budgets.
Everyone in your league paid their fee, they are allowed to play until they are completely eliminated.
Pro leagues follow the public league format, until that changes, you'll need to learn to deal with the "unclean" continuing to pursue victory.