It's offensive because JMS tried to defend this story as being a REBUKE to the "virgin/whore" dichotomy, by showing that even a "good girl" like Gwen had a sexual side, but in point of fact, all that it did was REINFORCE the "virgin/whore" dichotomy in her character, because the ONLY way that Quesada could imagine Gwen being anything other than a total virgin was if she had secret sex with the father of her then-ex-boyfriend's best friend, which is ill-advised enough in itself, even BEFORE you get to the fact that Norman Osborn ALWAYS had a 100-percent openly creepy personality, which makes Gwen seem both stupid and weak for swooning and choosing to go to bed with a man who projected all the warmth, compassion and trustworthiness of a convicted serial rapist. And since Gwen isn't even alive to share her feelings about it, it becomes exactly like identity Crisis - ie. a story in which a woman gets violated (Sue got raped, Gwen got used) and killed, and the story says that this is a bad thing because it makes the MEN feel bad.
Also, after Norman has already been revealed as the one who masterminded the "Clone Saga," AND abducted Peter and Mary Jane's baby, AND replaced Aunt May with a dying actress, AND killed Peter's clone-brother, AND briefly bought the Daily Bugle, AND was temporarily retconned into being the guy who sent all of Spider-Man's first enemies after him in Byrne's Chapter One, revealing that he also took Gwen's virginity, and that Peter never even had sex with Gwen, REALLY overplays how much he's become the singular source of every single one of Peter's miseries. The only way it could get any worse would be if they revealed that Norman hired the burglar who killed Uncle Ben and arranged for Mephisto to make the deal with Peter. Plus, Norman impregnating Gwen set the precedent for Norman to impregnate Harry's ex-fiancee Lily.
Oh, yeah, and with all of that, even after being caught and unmasked LIVE ON TELEVISION in the act of MURDERING COPS AND CIVILIANS, and then CONFESSING ON AIR to being the Green Goblin, Norman is STILL universally beloved by the entire public of the Marvel Universe, with Bendis saying shit in interviews about how Norman will be a better "hero" than the REAL heroes BECAUSE he's evil, while Spider-Man is now a loser who's more hated and put-upon than ever before. You'll forgive me if I question who Marvel is rooting for here, especially when Quesada gushes in interviews about Norman's "awesome hair" and his "intense sexual charisma," as though Norman is his damn Canon Sue.
I hate this story, and everything that's come from it, so much that I now wish that the character of Norman Osborn could be retroactively erased from existence - not just retconned from the comics, but all of his stories never published in the real world - just to prevent that one story from ever being told.
And if you find my posts so annoying, scroll past them, because you know by now that I'm not going to make them any less annoying to accommodate you (in fact, the more complaints I get on that score, the more I tend to amp it up, because I'm incredibly contrarian and spiteful).