This site has done really well with the mods and administrators it has. Most sites cannot plan for a attack like this one, this is not the usual spamming. This is one angry person, or several angry persons. Until they decide to take their anger back to facebook attacks they will just keep creating new SN's. The site could ban their IP's but most of these jerks use software to hide their IP.
Just be patient, some other site will PO them, and they will go bother them instead of us. I have a good guess who is doing it, but have no proof. Just the timing of it, and a member from the other gun site scolding his fellow members for it.
Honestly I do not see what they are going to accomplish by acting like spoiled children because others will not jump on their bandwagon.
The only permanent option I can see, I doubt the staff wants to do that, is to create a sub forum for long standing members. When the attacks come then we can completely avoid them. This has worked on other sites, the main subforums still remain active as that is where most members are. But when a problem arises it allows the flow to continue until the spammer gets bored and moves on.