Final answer:
It is true that unions should be cautious not to swap clearly meritorious grievances, as it may lead to a breach of their duty of fair representation, which obligates them to represent the interests of their members equitably and without negligence.
Step-by-step explanation:
True, unions must be careful because swapping grievances that are clearly meritorious may constitute a violation of the union's duty of fair representation. This duty requires unions to act in the best interests of the members they represent without discrimination, bad faith, or gross negligence.
Unions are important because they serve as a primary line of defense for workers against efforts by firms to suppress wages and benefits. However, union actions must be conducted in a manner that remains fair and just for all members. Any practice that involves bargaining away solid grievances for other concessions can potentially disadvantage some union members and lead to legal implications for the union.