Is it an offense to call a person a scab?

Yes, calling someone a "scab" can be considered offensive, particularly in the context of labor relations. The term is often used to describe someone who works during a strike or replaces striking workers, and it carries strong negative connotations among union members and labor activists. Using the term can lead to conflict and may be viewed as disrespectful or derogatory. Context and intent are important, but generally, it is advisable to avoid using such charged language.