It sounds so simple. If you want money from the US, then you must sign a pledge to not, in any way, support prostitution. Sounds so simple, while you sit on your Lawn Boy and mow your grass. Unfortunately not everyone lives in America and the money we are talking about is to prevent AIDs in foreign countries.
Here is an article on the matter and a film that opens up the complexity of the issue.
I can just picture some "Bishie" like Monica Goodling saying, "of course we should put this clause in the contract, what could be the harm in doing that?"