We see that in prostitution, in illegal immigrants working in horrible conditions, Dubai laborers[1], etc. In contrast, a Software Developer in the Bay area can hardly claim such conditions.
1. http://www.theguardian.com/global-development/2014/oct/23/mi...
Though if you'd care to expand, I'd be interested in your argument.
Then the argument is if a person is not forced into prostitution but chooses it as their livelihood, shouldn't it be acceptable?
If you want to prevent these situation you're describing, you need to give people a third option, that enables them to avoid the first two. Criminalizing prostitution will just harm those you want to help.
EDIT: from your other post, it seems we're in agreement.
Buying services and goods, on the other hand, is not violent, like rape is, although we could see the fact of poor people (or all people, really) having to sell portions of their lives to strangers to survive as unfortunate and alienating. This is, I think, where Marxism comes from.
I agree with what you wrote, of course. I may not like the existence of prostitution, but in order to have others respect my strange preferences, I'll have to respect the strange preferences of others, as long as it's consenting adults doing things.
I'm sold. We need a law against having financial dealings with poor people. Think of the children.