The people with that stigma aren't going to be looking at that content anyway.
They think it's immoral but they definitely still look at that content. For advertisers it's about brand perception and not appearing next to immoral content.
No, but they will gladly indulge in a bit of pitchfork-and-torchery when someone shares a screenshot on Facebook of a Proctor & Gamble ad for baby powder next to a young woman with pigtails and tube socks in the questionably named 'teen' category getting spit roasted.
Brands don't want to be next to content that has that stigma.