ok just checked into it.
So the webmaster of this website has chosen to block this webforum from being indexed in Google.
Its there in the code.
General info is here.
'Using meta tags to block access to your site"
But if you go to this webforum's root page
and then "view page source" you can see the webmaster put the "noindex" code into this website.
So this webforum is blocked from being indexed in Google.
<title>Cult Education Forum</title>
forum.culteducation.com/"/cache/bootstrap.min.js"></script><meta name="robots" content="noindex">
Its also blocking this subforum as well.
<title>Cult Education Forum :: "Cults," Sects, and "New Religious Movements"</title>
</script><meta name="robots" content="noindex">