Re: Poor Uncle Owen and Aunt Beru... Oh Well!
For all we know, Owen may just believe that Anakin was killed when the Jedi were hunted down by the Empire, so that's why he lied to Luke and made him accept as fact the much more boring idea that Anakin was a simple navigator on a spice freighter.
In retrospect, after Empire
came out, Owen's admission that he was "afraid of" Luke turning out like his father fit perfectly as one of the things in the original film foreshadowing the revelation that Luke's father is Vader. To me, that line really plays like Owen is aware that Luke's father turned out bad.
“A life is like a garden. Perfect moments can be had, but not preserved, except in memory. LLAP” — Leonard Nimoy (1931-2015)