That changed with Hatred in 2015. There have been a number of them since. It seems that anything that gives Valve bad press is on its shit list, even if the premise theme has been done before by a bigger or more well-known company stateside. If the upcoming Grand Theft Auto game has full frontal nudity and realistically depicted sex scenes, I doubt Valve would give it a second look.
That was ten years ago, there have been tons of really objectionable games on Steam in recent years. Eg I just checked and the game where you roleplay as Kyle Rittenhouse shooting protestors is still on Steam.
Per Wikipedia:
> [Hatred] was shortly removed by Valve from their Steam Greenlight service due to its extremely violent content but was later brought back with a personal apology from [Valve's co-founder] Gabe Newell.