What does "Copper Member" mean? Does this forum have a paid subscription or what? 
You've been here for nearly 6 years and still don't know what copper membership is? That's a little odd, but okay.
10 years ago, when the authorities started to hunt down torrent sites, they reached a point where they had difficulty closing these sites - they shut down one and 10 were born. Faced with this difficulty, authorities adopted another strategy: going after sites that listed links to torrents. In this sense, several forums and blogs were closed and their owners arrested/fined, for promoting torrent links. Note, these forums and blogs did not host any torrents, they only told visitors where to find the content.
For example, the biggest torrent search engine, which did not host any torrents, the owner decided to close the site, because he was about to have problems with the authorities. And all of this happened despite torrents not being illegal. The content of some is what they are.
The same can happen with mixers. The authorities' difficulty in closing mixers - associated with hacks - may lead them to start attacking forums, blogs or websites that promote these services. What the forum administration is doing is preventing something like this from happening to Bitcointalk.
For example, the biggest torrent search engine, which did not host any torrents, the owner decided to close the site, because he was about to have problems with the authorities. And all of this happened despite torrents not being illegal. The content of some is what they are.
The same can happen with mixers. The authorities' difficulty in closing mixers - associated with hacks - may lead them to start attacking forums, blogs or websites that promote these services. What the forum administration is doing is preventing something like this from happening to Bitcointalk.
An apt comparison. You can discuss warez and illegal file sharing here on the forum, but if you start linking directly to copyright material downloads, expect to have your post deleted and repeat offenders could conceivably be banned.
Obviously people can make the argument that mixers aren't technically illegal yet, but the authorities are certainly treating them as though they were.