I don’t think it’s strange that you know your family history in this case.
An outbreak during childbirth can be dangerous to the child, with serious complications even leading to blindness, which is crazy if you think about it. That’s why a doctor is concerned about an outbreak, more so than transmitting it to the child in general.
Your dad’s reaction isn’t so unusual, either. Many people believe that although herpes is incurable, that other than in the conditions of pregnancy it is nothing more than a pain in the ass. There seem to be no permanent negative health aspects other than very painful lesions (again: exception preggers). So your dad was willing to take that chance with his life partner. As I mentioned, I had plenty of sex for 9 months and didn’t contract HSV-II. I didn’t know it, but that’s not relevant here.
I see no reason why you should share your mother’s health history with anyone. The guy’s reaction of anger came from ignorance on herpes transmission and was unjustified. You could always retaliate just as immaturely next time and be shocked!, shocked! that he didn’t tell you he’s had the chicken pox (gasp!), which is yet another strain of the herpes simplex virus, as are shingles.