Maybe they are classifying it as "malicious" because of what they believe is done here, rather than that the site contains "malicious" code which might harm someone's computer.
Afterall, there is discussion about "cracks" and obtaining software on "side channels," which many in the business of making and selling software would consider "malicious."
The classification by Symantic will not stop anyone who actually wants to find this Forum and/or it's threads and post from doing so. I believe it has an exclusion list where one can mark sites they wish to vist as "safe."
Regards,