The opinion-page column "Let's End 'Righteous Isolationism' Against Vietnam," Aug. 2, extends the faulty logic used to justify trade with Red China to socialist Vietnam. Both nations are currently in possession of lands taken through international aggression (China invaded Tibet in 1951 and North Vietnam invaded South Vietnam in 1975 in direct violation of the 1973 cease-fire) and both maintain brutal police states. Further, Vietnam continues to thumb its nose at the US about the MIA issue.The author seems willing to turn a blind eye to these facts because the other industrialized nations are now trading with Vietnam. He argues that through economic contact our democratic principles will become a force in Vietnamese thought. Much stronger elements in the Vietnamese national identity include how American democracy had a hand in assassinating President Diem in 1963, supporting the horribly corrupt regime that followed, devastating their country, abandoning them in 1975 despite promises other wise, and sending the boat people back. To the ruling class, national pride rests upon the fact that tiny North Vietnam defeated and humiliated the mighty United States. It is dubious to suggest that economic relations can override the memory of what the US has done to them. Chris Schulten, St. Louis, Mo. Letters are welcome. Only a selection can be published, subject to condensation, and none acknowledged. Please address them to "Readers Write," One Norway St., Boston, MA 02115.