I don't know if you can call this a sexual fetish or not, more like a sexual lust. Some people do have sexual lust of the kind where one takes advantage of someone else because they can't resist. Rape is this type of lust, or chaining someone up in a cellar and rape them day after day. That is what taking advantage of the homeless is, basicly rape. Of course there are those who want to be taken advantage of, they want to be used, this is fetish.