While I do not defend Spitzer's conduct, I feel I must point out a significant difference in the cases, particularly to those with romantic views of prostitution as a victimless crime in which a willing buyer gives to a willing seller.
The problem with the theory is that there are many more willing buyers than willing sellers. In some cases, as in the highest end of the market where clients want intelligent and refined companions, this results in the market adjusting the price upwards.
But most of the time, this is not what happens. What happens is quite literally slavery. Women are held captive, physically beaten, starved, and otherwise systemically forced into the sex trade. Even countries where prostitution is legal, such as Holland, have in recent years set up units to deal with "trafficking in women" because slave traders bring in women to satisfy the "price sensitive" end of the market.
The prostitution rings prosecuted by Spitzer, as far as I can determine, dealt with "sex tourism, which constitutes taking customers to countries where primarily women, young girls -- but also boys and men -- are bought and sold and held in a condition of slavery.
It is hypocritical for a lawyer and politician who has made his reputation on ethics and ensuring that no one is above the law to violate the law himself -- and to do so consciously and repeatedly. But his previous activities in breaking up sex-slave rings fall into different categories all together.