He was watchin the feature film when he shoulda been watchin the trailer!

I dunno, it makes sense when you remember that Ren/Ben was born well after Vader/Anakin died. His parents probobly talked more about his turn-around in the end rather then give a kid all the details of all the horrible stuff he did, which means that the bulk of what Ren ‘knows’ about Vader likely comes from Snoke, a…

the top one is for your dignity