Please remember the difference between those collecting on the streets and the workers that are demanding the sex for food.
The person on the street will be a person who genuinely cares for the people/cause they are collecting for. The aid worker in country will more than likely be a local anyway. In these countries power is all, and the power to withhold food and get what ever they want including sex is particularly strong. The minority of genuine aid workers are not really in a position to stop this abuse, they have to go with the devil they know.
Reason enough to get soldiers in to control such activities?
Fair point MSR. As mentioned above, perhaps rather than the UN/League of Nations taking responsibilty for it they should give command and lead on an Op over to a particular country (UK,US, Germany, etc) with the other forces under them coming from other countries.