EMPEROR: Good. I can feel your anger. I am defenseless. Take your weapon! Strike me down with all your hatred, and your journey towards the dark side will be complete.
If the Emperor just wants to ensure a fight between Luke Skywalker and Darth Vader by telling Luke to "strike me down," (he knows that Vader will block Luke's swing) then why does he say the phrase in bold? You'd think that that would actually make Luke LESS likely to swing at him, which would mean there would be no fight between Luke and Vader.
Turning to the Dark Side should have nothing to do with the Emperor simply wanting Luke to swing at him and Vader to block it, thus starting fight. Right?