Wow. At first I thought this was a troll topic.
"Nobody could be seriously offended by this, right?"
The message is a lot like finger wagging. Like the game is saying "Oh you scamp. Getting into all sorts of trouble~" Honestly it's very silly that people are getting upset over this. It's tied to celebrity status, right? The media loves to jump on celebrities for anything they can think of. Child out of wedlock? Media would have a FIELD DAY with that one. Like someone said, Arnold Schwarzenegger got "slammed" as it were.
Let's look at it this way. What do you think your parents would think of you if you had a child without getting married? Yeah. You'd get berated for your lack of responsibility A LOT. If you claim your parents wouldn't care then you are obviously lying through your teeth.
My mother is a single parent. Is this offensive to her? No, she's a good person. It doesn't matter if she had me out of wedlock or not. She didn't but a few of you assumed that single mothers get shunned simply for not being married which is completely untrue.
Truth of the matter is people DO judge you for that sort of thing and they generally focus on the girl because SHE had the baby. Now the guy does get some flak too but not nearly as much. Don't know why but that's just how it is. Does that mean it shouldn't be in the game? No. If you are "in a loving, supportive relationship" then why don't you get married? It shows you're committed, provides all sorts of legal benefits, it's better socially and financially, not to mention it shows you love the other person. If you've been in a relationship with someone for nine months at least, I would expect SOME form of commitment. Otherwise, I wouldn't think much of their relationship which is probably why the social stigma exists in the first place.
Of course there are exceptions like rape victims, couples who have falling outs, etc. But we're talking about two, responsible adults who love each other and want to be together. Also Sim's.
Really, there is absolutely nothing offensive here and you actually have to work to get this message. First you have to buy the expansion to even have the message show up. Second, you have to actively work to make your Sim a celebrity. Third, you have to intentionally get your Sim pregnant with the "Try for Baby" option. Fourth, you have to wait it out and not get married. Fifth, you have to have certain character traits to even GET that message after all of this.
Besides, like I said earlier it's more like the game is wagging it's finger at you going "Tsk tsk" and the only punishment is being shamed for three days which is the common punishment for anything "bad" you do as a celebrity. At the end of the day, it doesn't affect anything other than your Sim's mood. There is no other "punishment" than that and it even goes away rather quickly. I'm pretty sure if this happened to you, you'd be in a pretty sour mood too.
"It's just a game, I should really just relax."