Just to put it in perspective. Thailand and the US have had almost the same number of AIDS deaths since statistics have been kept, about 600,00. However for 2007, the US had 65,000 reported cases and Thailand had 12,000. So you need to temper the hysteria of your friends with some facts. Is that still too high, absolutely, but is also too high in the US.
As for tourists ruining Thailand, if it weren't for tourists, Thailand would be even poorer than it is. Tourism is Thailand's number one industry. The sex industry started to really grow 50 years ago with the Vietnam war, so it is not a new thing.
Now if were so bad the government would shut it down. I believe the government knows how the Thai economy would collapse if they started enforcing the actual laws, which are on the books.
In Thai culture the children take care of the parents. The average income for Thailand, per the US State Depratment, is 3,700 a year. I am betting in the north it is closer to 1,000. A girl can earn 300 to 600 a week if she is good and pretty. It may not sound right, but it is the truth, that in one month she can earn as much, if not more, than her entire family can earn in a year. Many of these girls send a significant portion of their earnings back to their parents.
This is a real threadjack, but I had to responde to something I believe is wrong.
You are basing your entire statement on anecdotal stories from a few natives and the sensationalism that drives our media. Until you actually visit and see some of the beautiful sites such as The Grand Palace, the reclining Buddha and Wat Arun in Bangkok, you are only speaking of second hand knowledge and should temper your views.
After I come back from the Sunday errands I will post back on topic.