A restriction of the issue to that is based on an implicit assumption that policy choices have no effect on sex trade. But the point is that the policy choice of full legalisation subsidizes the 'industry'. Which also means more victims. Thus, for many, the effect of policy choices is not between slightly better or worse situation, but being made into a prostitute or not.

poverty that makes people do jobs that are degrading

It's much worse than that. Again, for the majority who were human-trafficked or tricked from abroad, this is not choice.

Giving residence permits and working permits and proper jobs to the women will reduce the pimps' profits.

As the German experience has shown, too, that's a false liberal hope. In a 'business' based on blackmail and threats, working permits are a paper and proper jobs a front, and legal safety in doing 'business' and reliance on state social systems increases pimp profits.

Encouraging the women to give evidence will increase the pimps' risk.

How so? If they can use the same extortion and threats as before (including the implication that they can't trust police as police is "in" on their business) to force the women to pretend to authorities that everything is voluntary and nice, it will actually decrease their risk. And that's the typical situation in all the stories on escaped girls, and the situation described in the above linked article, too.

This approach won't find the approval of the xenophobian mainstream

I'm not so sure. Bot the xenophobic and the liberal mainstream is just fine ignoring how all those East Europeans truly got into the 'business'. Not to mention the part who are clients.

_{*Lunatic*, n.
One whose delusions are out of fashion.}