Quote Originally Posted by mangosta71 View Post
Robert was willing to forgive anyone except a Targaryen. I suspect that his refusal to forgive them stems from his belief that Rhaegar kidnapped and raped his fiance. (We don't know if their relationship was consensual or not and we probably never will, but what matters is that Robert believed that Lyanna was forced.)
I think we'll find out from Howland Reed or perhaps Barristan Selmy or Jon Connington whether Lyanna eloped or was kidnapped (and whether Jon Snow is Ned's son or Lyanna's or. . . both! ). But you're right in that the truth doesn't matter as Robert (and Ned) believed Lyanna was kidnapped.