I never thought so.
But it is apparently far worse than the violence routinely experienced in video games. I don't have a problem with either one, but let's think realistically... how many gamers are likely to have at least seen some milk factories in their lives? Hell, plenty have a set attached to them. I think a very large percentage of us have seen and hopefully done more than that. Yet I'd wager my last Sovereign or whatever fantasy currency you favor, that very few, if any, gamers will have savagely butchered men, women, and animals with medieval weapons and spells. So devs and the ESRB are not afraid to show us what we've never experienced for ourselves (and hopefully never will), only what we have (or hopefully will).
I think one of the big problems with showing sex in games is that there are certain aspects of it that make it inappropriate for younger gamers. That's part of why we find pedophilia so terrible, and it's why statuary rape is even a thing--kids, and younger teenagers, are not mentally developed (the brain doesn't fully develop until about the very end of the teenage years), and this combined with sex can have unpleasant impacts on the young person's identity. And, for better or worse, game companies are recognizing that and tend not to put it in there. Conversely, there's very little that's ambiguous about violence, about death even.
Compare a "bad touch" with a slap to the face. The latter may hurt the feelings...but the former can have serious effects on the child's psyche.
I'm not saying that in-game sexual content constitutes abuse, but it can introduce people to things they're not mentally ready to deal with yet, and that's something developers take into account (yes, the kids shouldn't be playing the game, but no, that doesn't mean they aren't allowed to account for it, or for kids watching).