Easterhay said:
What?
By striking down Vader in anger, you're saying that those means would achieve the end of the Emperor and his empire. And I'm saying you're wrong, based on... well, take your pick, really, from various lines of dialogue throughout the films about striking out in anger and using your powers for attack, not knowledge or defence.
Those means could fail to bring down Palpatine and the Empire, but neither would those means lead to Luke joining Palpatine.