If he deems an issue valid, Sean Penn will make thetime to tackle it.And that’s no simple matter, given the active pace ofthe two-time Oscar winner’s career. Recently honoredagain as best actor for his title performance in “Milk,”Penn is both narrator and executive producer of “WitchHunt,” a documentary about several parents sent toprison in the mid-1980s for alleged child molestation inBakersfield, Calif.