I think no one is responsable for others behavior. Each people should consider or reconsider each time when they want to do something antisocial, or not such well seen in other people's eyes. Backpage.com fault is just of being one of those sites who is so permitive with adds. They should not allow people to post such easy the posts there. Women are being seen sometimes as goods in other people's eyes, so you need to be very careful when it comes to this kind.