"[Uncle Owen] didn't hold your father's ideals - he thought he should have stayed behind and not gotten involved."
Theres some good info about Owen Lars at the Star Wars.com Databank:
http://www.starwars.com/databank/character/owenlars/index.html
Apparently Owen thought Anakin should have stayed with his mother on Tatooine and not gotten involved with the Republic or the Jedi because of the affect Owen seen on his step-mother Shimi of being without Anakin. An older Owen did not want to see Luke leave Tatooine and possibly become a Jedi like his father because Owen feared that Luke may suffer the same fate as Anakin did. Also the Databank entry confirms an EU incident between Owen and Obi-Wan over young Luke, So I guess this confirms why Luke (in Episode 4) knows a Ben Kenobi but not an Obi-Wan Kenobi.