I don't see why this is true at all. I don't see how owners have any significant leverage and/or would be inclined to be any worse than other employers.
A restaurant requires significant investment, great chefs, R&D in dishes, menu, advertising, payment systems, liquor licences. 'Licensing' aside, a 'brothel' in it's simplest form can be pretty simple.
If it's legal and above bar, they are in the exact same position as most other workers.
I'd imagine the bar is not to high for a brothel license (could be wrong) - I don't see why even 2 or 3 women couldn't simply make their own brothel.
Also - I disagree with the idea that 'men' should be punished - this is a movement started in Scandinavia, where gender politics in legislation is getting outlandish. If society deems it an immoral/unsafe act they want to ban it (I'm not taking a position on that) - then both sides should be responsible.
I grew up in a 'single parent' household, my mother had very little in the way of skills - and we made it ok. I know quite a number of people in this situation. I reject the idea that in most cases that prostitution is some kind of 'end of the rope necessity' for women - it's a choice. Now - there are situations of 'sex slavery' and 'extortion' in which case it's really neither the women nor the buyers of sex that are at fault (unless the buyers know there's something wonky, but I'd imagine there's no way to tell one brothel from the next in terms of their 'employee status') - and these 'slave pimps' should be pursued more than anything. This is quite a problem among organized criminals in areas wherein there is high levels of immigration - I know it is in Toronto, Vancouver and Montreal. Women are unable to come forward because often they lack immigration status etc.. This is a serious problem, nearing 'human slavery' and it's 10x the problem in my books.
So to take such approach here, should a nation make a distinction between a brothel and a construction company? Both has a certain amount of work related injuries, exposure to hazards, and a long history of exploiting workers. A common law can regulate, monitor, and minimize those problems for all industries, and measure the success using establish methods. If workers are in a weak bargaining position then that is often the signal for nations to step in and demanding things like minimum safety rules, minimum wages, overseeing boards, and increased liability for companies.
The trouble with the New Zealand law [2] is that it empowers brothel operators. There's a presumption in the law that sex workers must work for a brothel. That put sex workers in a weak bargaining position. Nevada is like that, too. The UK, though, allows prostitution but not pimps or brothels. So it's all phone and Internet based.
(I had this explained to me by one of the people behind Prop. K, a high-end call girl who was also a labor organizer. Definitely not a victim. She wanted to empower sex workers, not pimps. But she was having a hard time getting that message across. At the city level, all they could do was reduce the level of police harassment, not fully legalize sex work. So they couldn't really make rules for sex work.)
[1] http://www.nytimes.com/2008/11/01/us/01prostitute.html [2] http://www.legislation.govt.nz/act/public/2003/0028/latest/D...