Like nearly all its investigative reports, tonight's Frontline deals with a national story - the overwhelming, controversial success of Wal-Mart. ... Is Wal-Mart Good for America? (9 p.m. today, KRMA-Channel 6) is anything but an esoteric documentary about a high-powered company whose association with consumers is irrelevant or secondary. While the title suggests the answer should be provided by viewers, the documentary's content offers ample ammunition for those who contend Wal-Mart's business policies do not benefit the nation's economy and the work force. Even with this biased angle, Frontline has produced a full-blown portrait of the growth of this business...