BOSTONThe Rev. Francis Sebastian's Sunday sermon condemning homosexual behavior was suspiciously rich in detail and nuance, parishioners from the Adoration Of The Savior Catholic Church noted Monday. 'For a celibate man of the cloth, Father Sebastian is very specific about which code words not to use on which forbidden chat rooms at which times of the night,' said Betty Riegert, 67. 'He also seems to have done his homework on what happens if you flash your headlights at certain rest stops along Route 16.' Riegert and other parishioners expect Sebastian to revisit his usual well-worn themes, 'Consider The Lilies,' 'Back Street Sodom,' and 'Christ The Bridegroom,' next Sunday. 