I think this was a common attack vector around then, but is no longer common.
Can you not detect and prevent this based on the HTTP referrer? Maybe reroute to goatse or something....
The last thing you would ever want to do is associate your domain name with gross, offensive content like this. The web is crawled all the time for snapshot data.
Additionally, you're more likely to cause your own (potential) users to stumble on this than anything else.
IMO, the best policy is almost always transparency. If you were to redirect users (and referrer-based redirects are a fragile thing), send them to a phishing/spam awareness page and explain that they most likely arrived from such a source.