KPBS AIRDATE: April 12, 2002 The cast comes down the aisles, steps onto the stage and faces the audience, glaring. They examine us, one by one. And then they launch into the hard-edged, aggressive opening number, "Come Look at the Freaks." And who are the freaks, anyway? The congenitally disfigured or their gapers and gawkers? This is just one of the powerful questions subtly asked in "Side Show,"