you may get that impression from the media and your own bias but it goes on all over this country and has more to do with machismo and the idea of men being in control than geography. This particular person is a criminal just as any common strong arm street thug taking advantage of the weak and defenseless.
I wouldn't disagree that sadly it takes place all over the world however I do think that in the country Sosua (and Puerto Plata) and Boca Chica surely get more than the average when it comes to sexual criminals from other countries. They probably don't speak the language, stand out if they are say in Cotui, plus given the in your face prostitution it attracts a certain element. There are enough "my fren" guys around that would probably help a perv like him find what he is looking for.