To request that a thread be closed we should send a private message to the moderator responsible for the forum in which the thread appears.
Since the thread you mention is in the Moral Theology forum, the moderator in charge is Julian Peters. Here is a link to his profile. You can send a private message from there.
For future reference, here is a link showing all the moderators and the forums for which they are responsible.
(scroll about halfway down the page)