Ya know, Lucas really messed up Kenobi
Kenobi, the glorified hero of the prequels, left Anakin (a child-killing mass murderer) injured and burning, but alive, and simply walked away. He didn't even put his former friend out of his misery, he didn't take responsibility for having trained Anakin, he didn't call down some assistance to see if Anakin could be salvaged... nothing.
THEN Kenobi decides to chill out on Tatooine for 20 years while his former apprentice is out there helping to destroy the galaxy and kill the rest of the Jedi.
When he runs into Anakin's son, Kenobi shamefully LIES and says that VADER killed Luke's father, because Kenobi is too afraid to admit that HE is the one who cut down Luke's father and then left him suffering. He can't admit that he basically ensured Anakin would be angry and traumatized and seeking an even greater revenge.