Before you say, "Why don't they just leave the relationship?" you have to understand that people in abusive relationships often face a greater risk of assault when they threaten to report the abuse or threaten to (or actually) leave the relationship.
This billboard makes a very broad statement. It uses people to make up the product bar code which symbolizes the people who are being sold through human trafficking in the sex trade. People don't have bar codes on them! People are not for sale!
I picked this ad because it shows a very disturbing picture of dead hippies being chained to a tree with master locks. This ad can be taken offensively because many people still consider themselves "hippies.