So it's ok that the same under 18 userbase is allowed to interact with simulated violence and gore but not with animated models doing mildly sexual things with each other?
I mean come on, if it is about the morality of the issue, they may as well remove the Sims! That has simulated sex and with a few clicks of a button that handy mesh can get replaced as well, for nudist colony Sims.
How can anyone take offense to this? No one is forcing you to play it, just ignore it if the sight of pixelated penii and pussy offends thine eyes. Don't even think about leaping to the "but the kids!" argument either, censorship is in place and if your kid ends up watching porn then the onus is down to you as a parent not doing a good job. If a kid is going to go out of his way to get this on a Steam account, I think he is going to be far more resourceful looking up actual Internet porn.
/sigh, when did society start becoming prudes again?
Just as a side note, I have no intention of ever playing this game, the content doesn't interest me in the slightest. It just amuses me that people get their panties in a twist over what other people want to watch because it doesn't agree with their good wholesome public values (which go out the window come woohoo time at home, amirite?).