So we are upset about Slap Hillary, which was put up by a a group called, "Republican Super PAC." They state, "We didn’t see the liberal media bemoaning this “Slap Palin” game when it came out!
They only care when it’s the candidate they support for president." (http://thehillaryproject.com/games/
The difference is this. As near as I can tell, the Slap Palin URL and website is not associated with a specific political party/PAC. There is not a party agenda, or political force behind the game. Both "games" are reprehensible, and I don't think any women's rights advocates would argue that either is acceptable. When a national organization that is openly attempting to influence upcoming elections through the depiction of violence towards women, I get worried.
We can be reasonably sure that the coordinators of this group are Republicans, probably with serious political influence. Violence against women is a real thing and should not be condoned in any way shape or form by those individuals supposedly "leading" our county.
TL;DR - The problem is that a super PAC is depicting violence against women, not that it's been done before.