yup. there's a whole bunch of people who will cry 'but this slippery slope' - sorry your incest twins use too much lube, that freaky slope is your problem, not Steam's. get over yourselves. it's a private company, nothing compels it to carry your daddy twins incest shit.
It doesn't matter what was banned. It could be the most heinous shit imaginable and payment processors dictating what is allowed to exist would still be horrible.