Just block them, there is a filter system in your Google Adsense Account area! Google Adsense is to big to stop everything , you can try reporting the Adverts as well!
Well not exactly porn..... but i agree that google should allow u a choice of what types of ads you want to accept although this is a indication... u need better keyword capability on ur site
atleast you are not getting ads that are selling green cards -_- or like those.. find ebay ads.. Find "Jews" on Ebay, Find "Fruad" on Ebay .. ect..
if some is promoting dating, then its not porn. whether is straight, gay, or lesbian dating - it can be legid site based on content. if the site contains no nudity and provides resource and reviews to dating sites, then its fine
Really wierd, some clever webmaster must have fooled Google. I think until Google takes some action, you should remove the ads / move to image only ads so your reputation / userbase does not get affected.