"...Comon, these things are contrary to everything you have ever known your entire life, maybe you had some idea that your uncle wasn't quite telling you everything. It is clear that Obi-Wan was trying to protect Luke. Also you can see from Episode III that the whole thing was prettty rough on Obi-Wan emotionaly. He has had plenty of years living alone in the dessert to reflect on the tragic turning of the man who was like a brother to him. You don't even need the line of Yoda telling Obi not to let the children know of their true parentage. It just isn't needed. Probably Obi-Wan has consoled himself through the years saying that Anakin died the moment he turned to the dark side. It isn't that Obi is merely lying through his teeth. Also at this point Obi-Wan believes that Luke is still unkown to Vader. "
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Opinions will vary, but it comes down to how "honorable" you think it is to lie.
Look at it this way: Lying is dishonorable and only justifiable if there's some greater good to be served.
Lying to Luke served what greater good? Did it prepare him to face Vader? No, it opened up a great opportunity for Vader to undermine everything Obi Wan and Yoda taught him. Did it protect Luke? Protect him from what? He is not a retard or a psychologically imbalanced infant -- he sees his uncle and aunt, the only parents he's ever known murdered and that only inspires him to do the right thing.
Any presumption that Luke can't "handle the truth" flies in the face of everything Luke Skywalker does. The guy blows up the fu*king Death Star, I think he can handle an unpleasant truth about his father. Plenty of murderers have children. Those kids know about their parent's past and if they have good guidance and strong character (as Luke Skywalker CLEARLY HAS, Ben is a Jedi Knight afterall) -- they often turn out to be steeled in their resolve to avoid the mistakes of their parents. There is no statistical evidence that killers will have evil children who fall to the dark side. It's nonsense to say Luke is being "protected."
What is protected is the "secret" which was revealed in 1980 -- a secret that was NOT PART OF THE STORY when the first movie was made. Vader became Anakin Skywalker in Draft 3 of ESB. They played fast and loose with Ben's story and let a lie stand and explained it later as "the truth from a certain point of view."
But they never explain why the lie needed to happen -- they only JUSTIFY the lie in retrospect. Why? Because the lie did NOT need to happen. It WASN'T a lie until Vader was changed to become Anakin.
This may sit fine with you, but it tinges everything Obi Wan does in the OT because he is pointlessly dishonest with Luke, sets him up for a horrible fall, and never gets around to giving a decent reason why he did it.
But that's not the official view of this thread, of course. It looks like the lie will stay. I will agitate for a line that lets Yoda explain the necessity of the lie ahead of time in Episode III like "Know the truth, they cannot. Like a beacon, their emotions would be. Find them, the Sith will if told they are." THEN Obi Wan will actually be protecting Luke from something -- but without that reason, it's just convenient for the story to make Ben a liar -- and that's the only way to put it. He LIES. It gains him NOTHING. And he NEVER EXPLAINS WHY.
SORRY for all the CAPS -- I find that people never address these issues in trying to justify their affection for the lie as it is.