1. Economic is a horrible reason to allow human trafficking. First, I'll refer back to "consenting adults". It's different throughout the country. Regardless of what anyone else thinks, I don't really have a problem buying a shirt from a 16 year old at Old Navy but it seems awful sleazy to buy some legal poon from the same girl. If that's not going to be legal, you'll have to explain why. Tax revenue would still be generated by this "consenting adult'. Second, I'm not sure creating tax revenue is a reason to legalize anything. Maybe we should just tax baby-making. Tax pet ownership. Tax parties thrown at your home. In fact, let's tax everything. That would create plenty of tax revenue.
2. Public safety, as you state it, is also a horrible reason to legalize human trafficking. Desensitizing us to sex, which is a pitfall of prostitution, will desensitize us to other things. Like the whore's feelings. When they don't do what they're told, those prone to violence will simply smack them in the mouth. After all, they're being paid to do what we want. With more people getting the sex and caring less about the other person, I somehow doubt violence will be reduced. The police may as well set up a station in the whore house. I'm not sure we "waste" less resources at all. As for STDs, I honestly can't deny that legalizing prostitution should reduce the risk. I don't really know the gestation period of STD's but I assume the 'hos won't be tested daily. I'm pretty sure street 'hos use condoms and I'm pretty sure the legal 'hos would be required to do the same but, on the whole, the legal 'hos will be tested more frequently.
While those two very real "impacts" for the legalization of prostitution aren't very real or impactful, they would change the culture I'm pretty sure you can't deny that. If you can, please try to explain.