The etymology definition of scab is described as "skin disease" and "itch".
Scab is also a term used to describe people who would replace workers on strike. A scab in the workplace is looked down upon because they are not team players. While union members are on strike, scabs fill in their spots and sabotage the cause. More broadly, scabs are people who do not participate in industrial action. The unknown citizen is not a scab. Therefore, the unknown citizen contributes to industrial action.
Scab is also a term used to describe people who would replace workers on strike. A scab in the workplace is looked down upon because they are not team players. While union members are on strike, scabs fill in their spots and sabotage the cause. More broadly, scabs are people who do not participate in industrial action. The unknown citizen is not a scab. Therefore, the unknown citizen contributes to industrial action.