And maybe that's okay, too, but high school isn't the only place that many students will get to experience Shakespeare and if it can't be done right there might be more damage than good done.
There is a difference between not exposing a student to something that they cannot understand at first glance and not having a teacher who doesn't understand the matter themselves try to muddle their way through a presentation the material. Making it part of standard curriculum means that we will have a heavy dosage of the latter, whereas making it optional means that only those teachers who truly have a passion for the thing will present it (theoretically, of course).
Then again, I'm in America so our teachers don't have time to teach anything that isn't showing up on a standardized test, and for me this debate is purely academic :)