re: Crackpot ASOIAF Theories SPOILERS

If you think about it, not only did Rhaegar cause Robert's Rebellion, but, in a way, was a cause of the demise of the North in the War of the Five Kings. Had Rhaegar not run off with Lyanna and impregnated her, Ned would never have had to lie about spawning a bastard that caused great hardship to Cat. So, Robb sees what happened when you "dishonor" a girl out of wedlock (even though Ned never did it), decided to marry her and set off the chain of events that led to the RW and the fall of the North.