Everyone is responsible for the predictable consequences of their own actions.

If I pick up a rock, and throw it in the face of my neighbor, and then turn around and say to the horrified onlookers:

"look, people have been throwing rocks for a long time... if you want to hold me to account for my actions here today, first you're going to have to deal with every other rock thrower that ever lived."

The onlookers will be understandably horrified that this is my position.