You were doing them a solid when you told them that it was offensive. A lot of people would say "well this other romance book does the same thing--so it's OK for this genre" when it's like...if you go by that metric you can say literally everything ever written is OK. Because everything has been written. But offensive things don't stop being offensive to other people just because the author themselves might think it's OK. Doesn't matter if you call a serious crime a "kink" or if you try to redirect blame on the person critiquing you--if you offend someone, you can't click undo. that's their feelings, not the authors, and like who are they to tell you that rape culture is fine in erotic fiction and that you shouldn't be offended by it.
And like...most readers if they read something offensive on the internet just click away, unsubscribe, that sort of thing. Very few people would speak up about their free online fiction and say "yo freakin stop." So again, you did them a solid, because their readers that will leave once the forced pregnancy happens, will not. They will just stop reading silently and never come back. Since you are their critiquer...it is your job to bring up if something is offensive in the fiction.
And like this a thing that makes people stray from reading romance in online fiction, myself included. When this becomes so freakin common, it can just make you turn off of a genre entirely.