This is a strange case. Apparently, a judge decided that raping a prostitute constituted simple theft.
The argument for this, of course, is that she had already agreed to have sex with him, he just made her do it without getting paid, so in essence he simply took her money away. Yes, a woman can change her mind, but she didn't change her mind about the sex except to the extent that she didn't want to do it without pay. So in essence, the only difference between what she would have done and what he forced her to do is the lack of pay.
I think the relevant distinctions here are (a) the man took out the gun to force her to have sex rather than after sex in order to force her to leave without getting paid. So in essence, he didn't rob her of money, he forced her to do work after she said she would not. Forcing service under the threat of bodily harm is more akin to slavery than theft. (b) He forced to have sex with four men when she had only agreed to have sex with two. Seeing as she had never consented to having sex with more than two men, it cannot be said that she would have if he had paid her; therefore, the net effect may have been more than just taking away her revenue.
That is all.