It was only a matter of time before it happened and now it has.



Groupon is offering discounted tours of the historic armory turned porn studio Kink.com in San Francisco.



And like all things San Francisco, the promotion is drawing protest.



A group called the War on Illegal Pornography has called for a boycott of the the Chicago-based group discount site over the promotion.



Under the deal, Groupon San Francisco is selling passes for a 90-minute tour through five floors of the historic building in the City's Mission district, which is now used to film pornographic movies.



Patrons, who must be at least 18, will also be walked through "elaborate adult-film sets" by Kink.com employees.



Over 120 sets of two passes have already sold for $28.



The anti-pornography group is asking its members to sign a pledge vowing to boycott Groupon as long as it continues the promotion.



When confronted about their choice to feature this company, Groupon defended it saying "We thoroughly vet the businesses we feature. Fortunately, this business has proven to be a responsible member of their community."



For its part, Kink.com has been offering tours of the building for years. The tours were initially offered for free before the adult movie company began selling tickets because of the high demand.



The porn studio has also tried to get involved with the community by offering to open up the old armory and allow it to be used as a community center.

