Where there is no free will, there is no sin. Someone who is forced into sexual relations is not a sinner but a victim of someone else’s sin.
Someone who does not fight off an attack or cannot prevent an attack from occurring has not sinned. Fighting off a sexual attack even to the death, rather than allowing a violation of purity—as did St. Maria Goretti—is indeed heroic. Her willingness to fight to the point of death can be an inspiration to all who are threatened by sexual violence. Yet her willingness on her deathbed to forgive her attacker and to desire his salvation was an even greater act of heroic virtue.