Are you referring to turning down invitations or offers and if that has an effect on the freelancer’s Job Success Score? If so, then no, declining invites, offers, or withdrawing proposals doesn’t affect Job Success Score. If you’re referring to something else, please let us know.
Are you saying that there's something inappropriate about the project? If so, you should report it using the "flag as inappropriate" link at the top-right of the project page.