Luke needed experience and training.
They could have sit down and discuss all the shit happened before, during and after the clone wars. There was just not time for that.
Luke: "Why cant I use my hate to give me focus?"
Yoda: "It is dangerous"
Luke: "Why?"
Yoda: "It will take you to the darkside!"
Luke: "How do you know?"
Yoda: "Many padawans that path have gone. None return have!"
Luke: "Luke who?"
Yoda: "Well. Not many in my lifetime there were. Extinct the sith were you see!"
Luke: "So you knew no-one who defected to the darkside?"
Yoda: "A few I did..."
Luke: "Who?`"
Yoda: " Important it is not..."
Luke: " No, tell me! I wanna know!"
Yoda: "Yrmh. Count Dooku away turned. Darth Tyranus he became."
Luke: "Why?"
Yoda: " *sigh* When master Qui Gon died. Soon after he left. Lost his faith for the Republic we thougt. A politician he became."
Luke: "Who was Qui Gon."
Yoda: "Obi Wans master he was."
Luke: "You mean he trained him? Obi Wan told me You trained him!"
Yoda: "Yes yes. All of them I trained. When young they were. Padawans have their own master."
Luke: "So who was Qui Gons master?"
Yoda:" Count Dooku it was..."
Luke: "And his...?"
Yoda:" I was..."
Luke: "So. the Only jedi to turn to the darkside during your 900 year life was the ****ing one that you trained?!?!"
Yoda: "No! Not only one! *heavy sigh* Many more there were."
Luke: "Like?"
Yoda: " Anakin Skywalker."
Luke: "Who was he?"
Yoda: "He was Obi Wans apprentice."
Luke: "Why did he turn?"
Yoda: "He was seduced by his friend. Suppreme chancellor Palpatine"
Luke: "Who was Palpatine?"
Yoda: "He was the leader of the senate. And he is the evil Emperor!"
Luke: "So. Why didnt you kill him?"
Yoda: " Tried I did but little success I had."
Luke: "What about this Anakin then? What happened to him?"
Yoda: "Hi fought his master on Mustafar."
Luke: "Where is Mustafar?"
Yoda: " A lavaplanet it is."
Luke: " So did Obiwan kill him?"
Yoda: "No! Wounded only. Now he is half-machine!"
Luke: "right... I wonder what his family thinks about it."
Yoda: "All his family is dead..."
Luke: "What about his father?"
yoda: "There was none."
Luke: "How is that possible???"
Yoda: "Know that I do not."
Luke: "How did he born then?"
Yoda: "Midichloridians did the trick. Yes. Midichloridians!"
Luke: "What are those?"
Yoda: "Little things in our blood they are. Allow us to communicate with the force!"
Luke: "Do I have them?!"
Yoda: "We all do."
Luke: "Did this Anakin have them?"
Yoda:" Yes he did."
Luke:" What was his last name?"
Yoda:" Yrmgh.. Not important is that,"
Luke:" NO! Tell me!"
Yoda: " A skywalker he was"
Luke:" WOW! What a coincidence!"
Yoda: " yes. yes. But now we must eat."
Luke: "No wait. How exactly did Palpatine lie to Anakin?"
Yoda:" Offered his wife a chance to live."
Luke: "Who was she?"
Yoda: "Padme Amidala she was. A skywalker later".
Luke: " Did they have children."
Yoda: " Yes. Twins they did have..."
Luke: "What happened to those?"
Yoda: "Away they were taken. After Anakin defeated was."
Luke: "where???"
Yoda:" The boy to Tatooine sent was. The girl on Alderaan."
Luke: "WOW! This is creepy."
Luke: "Where was the boy placed."
Yoda: "To his uncle we sent him. A farmer was he. To hide from his father!"
Luke: "Wow. I am a son of Darth Vader?!"
Yoda: "****. Slipped that I did..."
Luke: "No! Tell me more about the darkside..."
Yoda. "The darkside is about... blah blah"
So I think Yoda did the right thing.
"No! No! There is no why!"
That way everyone is happy.