It depends but 5 reasons could be 1) They picture themselves in the other persons shoes, and they know they would want to fight back. 2) They know that violating others isn't kind or rightful so they stand up against it. 3) They now want to help defend those who are being violated, because they would want someone to do the same for them. 4) They naturally have a gift of advocation and fighting against unfair people. 5) They have had their rights violated before and can connect to other individuals facing the same struggle.