If this is not a unique case, and people posting statements that "Hey, I know a software by which you can hack into wifi servers" or "If you mix bleach with vinegar then you can make Chlorine" or "I've written a script which can hack wifi networks" and such were getting punished on regular basis, then certainly what you've said makes sense.
Maybe, I've been ignorant but I haven't seen a majority of such cases. Also, doesn't punishing the owner of forum makes much sense? If there is any actual potential threat, then it would the makers of website who actually gathered all these people. Not the people who are ignorantly making statements on website.
I'm just stating my personal opinions, but an action of seizing a domain, just because the seller, while trying to sell the domain, said that you can make profit from it in bad faith, without taking any actual steps to accomplish it, (like making such website) seems to be an over exaggeration. To me, it seems like government just wanted to show to the people that: Yes, we are working for great cause by going undercover and stopping any potential threats that could cause harm to the community.