Saga Luke's Childhood - A Tactical Error ?

But I think everyone has to come to that point at some time or another. Everyone has a dark part of them that wants to lash out and destroy the objects of their frustration. If you don't ever confront that part of you, then you can't ever overcome it. The more you deny your dark side, the more it's able to control you. That's why Luke reacted in the way that he did. He never acknowledged or confronted the part of him that wanted to kill his father for all the pain he put Luke through, and so he never developed the tools to work through those feelings. And so when Vader angered Luke sufficiently, the murderous father-killing part of him came out in full force, with no restraints.

I don't think there's anything dangerous or wrong about Obi-Wan wanting Luke to confront that part of himself. That's part and parcel of what it means to "confront Vader." Luke has to confront the Vader that's inside of him. That's what the confrontation in the tree in TESB is foreshadowing more than anything else.

This is also what Dave Filoni, after extensive conversations with George Lucas about the Yoda arc in TCW, said Obi-Wan and Yoda were doing:

"They never tell Luke to actively go out and save his father. In fact, they say he’s probably going to have to destroy his father. But it’s mainly because they can’t tell him that which he needs to understand — the true enlightenment of “I have to save my father.” They can’t just say it. That makes it easy. Faith isn’t about knowing."

Yoda and Obi-Wan can't just tell Luke what he has to do. Luke has to earn that knowledge for himself. Yoda and Obi-Wan are wise enough to know that they have to play the part of the out-of-touch authority figures whom Luke must surpass, even if they really do know better.* If they had just told Luke everything he needed to know, it would have been even more dangerous, because he would have thought he understood what to do, even though he really didn't. Because the only way to truly know the right thing to do is to experience the consequences of doing the wrong thing.

*And of course Obi-Wan knows better. He reached the ultimate state of enlightenment by attaining a state of infinite selflessness and compassion. He's literally the Force.