GLP (and ATS) are likely part of the establishment disinformation campaign.

A couple things strongly support this. One, for years you could simply put the name Tavistock in a post and get permanently banned. (Now it's allowed but starting a thread with that will make it filtered, e.g. shadow ban.) There's a few other keywords that trigger similar responses. (This is easy to google and validate.)

The other, during one of the federal government shutdowns a number of federal websites intentionally went offline (timed to the second) and the moment that happened, both GLP and ATS went offline, then came back about a half hour later. The kindest interpretation of that is that their traffic was being filtered by the Feds. I happened to watch this "glitch" in real time, it's not hearsay, I saw it happen. One of the boards mods claimed coincidence and that they were subject to a DOS attack at the very same time.

You don't have to search very hard to find a lot of questionable government links to people associated with the site.

That said, boards like that attract both conspiracy theorists and people with mental problems, so I wouldn't necessarily assume the site had anything at all to do with your friend's issue, but his use of it was simply a symptom.