I have heard a few people question the contention that the league should open its books to the players. The argument goes that no other business opens its books to its employees. I understand the argument, but I do not find it particularly compelling.
Just because other businesses do not participate in this act does not mean that is the right and fair course of action. It just means that other businesses do not participate in it. In most other fields of work, union employees do not have skills as in demand as NFL players do. It is usually easy to find a reasonable imitation of the skills involved. That does not exist here. Fans want to see the most talented football players. The players have more leverage.
Them seeking to use this leverage to look at all of the league's books seems fair to me since the owners are complaining about the old deal and saying it needs to be fixed. It seems reasonable in other fields. The workers just do not have the kind of leverage to make it happen.