Apparently doing things you know are wrong[having sex with trafficked women] is just because men need sex. More than integrity, decency, etc. Men don't need pesky things like empathy[what if I was in a foreign country, didn't speak the language and some stranger was trying to rape me up the ass?] or thinking before acting [you know, if going to prostitutes makes me feel bad, maybe I shouldn't do it] If women were men, this would be considered proof of inferiority- 'women can't control themselves! They'll do illegal, immoral stuff just because they can't keep their vaginas to themselves!' We'd hear about how women shouldn't be in high office, if they can't even keep themselves from cruising the ads in craigslist, placing a call, and setting aside the time an money to visit prostitutes! They just can't control themselves!
Of course, if men don't want to stoop to abusing women on the street, they can go and buy a creepy robot! or they can hump a pillow with the image of a young girl on it. About the why- I think there are probably many different whys. Some want to dominate, some are so stunted and broken by the patriarchy that they can't truly relate to people- a man can only relate to their 'inferiors' i.e. women by sex. It's like how men are trained to replace emotions like sadness or vulnerability with anger.
The desire to be with people is replaced by sex. And sadly, the sex that is sold to us is joyless. Robots with one word personalities aren't far off from the dull mass produced pornography that is seen as 'sexy' nowadays or contrived 'girlfriend' relationships in which a man pays for a shallow imitation of intimacy.
People long for joy, for true intimacy, but they can't receive it by paying for it. Making oneself vulnerable to real relationships with real people is scary, but I don't think that puerile fantasy can sustain them...