Ah, great, another company that wishes to profit off content while attempting to wash its hands of the implications of that content. Offering something for sale on a platform, or store, or "aggregator" as we're now calling it, is endorsement. If you take their money, you take the rest.
Personally I applaud Steam for their willingness to let adults make their own decisions about what content they want to purchase and consume, rather than outsourcing that decisions to the loudest mobs. Given the nature of modern society I've no doubt that Steam will face attacks from many, like yourself, who would prefer that Valve act as the Thought Police. I'm hopeful that they have the backbone to stick with this policy and weather the storm.