The rule of thumb for Religion Forum threads is to lock and not pull because some posters put a lot of effort into their replies which they or other posters or lurkers may want to bookmark for future reference. If the thread is mostly empty, a troll thread, duplicate, etc. it might be pulled.
I will put a note to the mods on the thread you linked to not pull it, since it has been used as an argument here.
Thank you.
The rules really do work well on Free Republic.