I've never understood why so many people have such a big problem with a little bit of railroading. Knights of the Old Republic and Mass Effect "railroad" the player quite a bit, and that allows them to tell an excellent, well-oiled story. A GM should be as flexible as their plans allow, but if you have a big, epic story you want to tell in the universe of Star Wars, your players will get more enjoyment out of that than they would if they were allowed to wreck all your plans.
A sane GM would never allow Luke to Charm Palpatine into letting him live.