it's a sad story... I have a site about icons and icon editor in English and Czech and I created a directory for webs related to computer graphics and now I get about 50-100 unique Czech visitors per day interested in those damned wallpapers. That stupid directory page on wallpapers is getting more visitors than the rest of the site. At least from the search engine. And to make it even worse, Google Adsense is showing PSAs, because nobody is advertising for the relevant keywords in Czech!
MAybe you should add more alternative content to your site and try to funnel those precious visitors towards it? Apart from anything else, Adsense isn't the only ad that can be displayed on a website -- sign up for some of the affiliate operators like CJ and show their ads instead.
I used to hate my visitors as they all arrived looking for non-existant porn via search engines. Some of the terms were disgraceful. At one point I was #2 somewhere for female arses. I suppose I dug my own hole by calling the title tag : Dirty Dio Bach's Web Fun - Porn Free Goodness From The Arse End Of Wales... Never again though - that was a lot of disappointed surfers...