For whatever it's worth, Nicholas Hytner, the director of the original production (though certainly not the final authority on the subject) has this to say in his memoir Balancing Acts:
"I'm not crazy, in retrospect, about the scenes in Miss Saigon that conveyed, accurately enough, the putrid atmosphere of the bars. I hurled everything I knew about staging at a script that had very little in the way of stage directions; the result had a relish that sometimes crossed the line into vulgarity. Clubs, bars and brothels have become staples of musical theatre. Some shows are aware that they aren't necessarily good news for the women who are supposed to work there, but musicals always want it both ways. What's not to like, they say, about a beautiful chorus girl in a bikini? Though please feel free to deplore the men who pay for her."
I think that's a good way of putting it--while yes, the show does condemn the sleaziness of the white men and encourage empathy with the Vietnamese women in the piece, the reality is more complex than that.
As for this idea of "truth" in representing history, I think that if truthful historical representation was the highest priority for the creatives, they wouldn't have engaged in yellow-face in casting the original production.
There's a lot that I like in Miss Saigon--the spectacular stagecraft and the stirring pop ballads--but it's important to understand how this piece has been received by the people it represents and the people who have done the work of putting it onstage.