I don't think obligated as much as they should not be concerned and there should be no backlash to them for stocking it as long as its separated appropriately. Video storms had porn rooms in the back of the store with some signage and people seemed to be able to handle it and get its an adult thing. Heck maybe even have a second but related steam.XXX site where you have to do bullshit verification to peruse. Then require any game that goes over some threshold of whatever to only be visible there. people can login with their steam accounts and have them connected provided they jump the additional hoops. these things are not impossible to work with.