You are the one who brought up watch forums.
Watch forums are generally operated for the benefit of their owners and sponsors (Omega Forums being an exception on sponsorships). They have the right to ban anything. I know of several forums that do not even allow linking of outside URL's.
If a forum is sponsored by a watch manufacturer (which a few are), then I can understand the decision not to allow the defendant in a lawsuit, or anyone selling that defendant's brand of watches to sell on their website. If the site is sponsored by an AD, I can see the same thing happening on the grounds that sales of "Homage" watches that are the subject of litigation could damage the AD's business and cause that AD to withdraw their sponsorship.
What I have not heard of is a non-sponsor manufacturer suing a forum for allowing the sale of homage watches where there was no implication that the watch was anything other than what it is. I know there was an issue at one time between eBay and Cartier regarding the use of the word "tank" with respect to listings of small, square watches not manufactured by Cartier. I believe they reached a private settlement on that issue. But eBay is not a watch forum.
Neither is the defendant in the suit you mentioned.
gatorcpa