"Your father wanted you to have this when you were old enough, but your uncle wouldn't allow it. He feared you might follow old Obi-Wan on some damn fool idealistic crusade like your father did."

Alright, apart from the undeniable fact that Anakin never once said he wanted Luke to have his lightsabre when he was old enough, and apart from the observation that Ben is being very sly by trying to put a wedge between Luke and Owen...what `damn fool idealistic crusade' is Kenobi talking about?
Is this a reference to the Jedi's hunt for the mysterious sith? Or an adventure they shared during the Clone Wars? Or is Ben, as he often seemed to when talking to Luke, just telling things from a certain point of view?
We've had this speech of Kenobi's in our heads for 28 years - but what is Ben referring to?