Could anybody tell me what this means? Thanks a lot!

What do the bolded parts mean? what is the author trying to express by saying
What reasoning could have prompted such advice? and a tawdry tip.

a little bit context:
The guidebook cautioned, however, that "telling the Vietnamese you are single or divorced will disturb them greatly. Not having a family is regarded as bad luck, and such people are to be pitied, not envied."

Fortunately, the book's authors had a solution: "If you are young and single, simply say you are `not yet married' and that will be accepted."

But I was 48. "If you are over 30 and unmarried, it's better to lie."

Ethically, I have a problem with lying, especially to foreign hosts. Realistically, I have a bigger problem: I am a pitiful liar. What reasoning could have prompted such advice?

"Divorce is scandalous," the book concluded. "You'd be better off claiming your former spouse died."

To this day, I don't believe I have ever read a more tawdry, coldhearted and insensitive, not to mention brilliant and satisfying, tip in any travel guidebook.