? about becoming a jedi

hey guys i just watched return of the jedi and something yoda says confused me. I have watched all the movies many times and never gave it much thought but it seems to go against what a jedi is.

Before he dies he tell Luke that he must confront Vader then and only then a jedi will he be.

Why must he do this to become a jedi. If he goes to face vader isnt that an act of aggression and doesnt yoda say that aggression is a path to the dark side.

What about all the other jedis that became jedis they never faced Vader.

 

He must face Vader to complete his destiny and save the galaxy.
All Jedi apprentice must overcome a challenge before becoming a Knight. Vader is the challenge for Luke.

-Seldon

 

He must also prove that he isn't afraid of Vader. Because fear is a path to the Dark Side.

 

all jedi must pass a challenge

 

It's his trials.

 

well once he does that then he knows the truth and will have more reasones to be on the light side