Wolf: By that argument, you are positing that “frum” clothing stores could sell miniskirts and sleeveless shirts or any pritzus of their desire. Sorry that does not “cut it.”
I again stress (a separate point) that when someone sins in regards to tznius, they are not only going to pay for transgressing the law themselves; they are going to be held responsible in the court of courts for the transgressions of thousands of others (passersby) made by her enabling them to see her in that state of undress. Even for that fleeting moment of seeing her, before quickly turning away from her pritzus state. (Of course if anyone looks any longer than the moment to realize her pritzus, it will cost them in court too.)