Thou shalt not broadcast a Semitic-themed show on Friday nights while we are in synagogue. That's the battle cry of at least some viewers including several rabbis who are complaining about CBS' decision to broadcast Brooklyn Bridge not only on Friday nights, but at 8 p.m., when Sabbath services are in session and Orthodox Jews are not allowed to watch TV. Created by Gary David Goldberg, starring Marion Ross and Danny Gerard, Bridge is a drama that centers on a Jewish family in the 1950s. ''Either it's a bad joke, or an act of covert anti-Semitism, or stupidity on the part of the network, and I think it's stupidity,'' says Richard Address, a prominent Philadelphia-based rabbi, with a laugh. Responds a CBS spokeswoman: ''As a network, CBS is committed to finding the broadest audience for all of our programs. Friday night is the best place on our schedule for Brooklyn Bridge.'' But even if it were moved to another time slot, says Ruth Paris, assistant director of the Council of Jewish Organizations in Flatbush, Brooklyn, ''Orthodox Jews are not going to like it anyway, because the lead character dates a girl who goes to Catholic school.''