I think this is fascinating, though that's probably because I'm a law lecturer. I don't do IP at all, though, so have no particular insight.
What strikes me as the most likely legal position, though, is this:
Lone Wolf (probably) have a clear case against various people who have created "My New Army Builder" tools. If they want to send letters, or set lawyers on, people who have infringed their trademark in this way, that's entirely proper.
What I don't quite understand is where Privateer Press has done anything wrong at all, or why Lone Wolf thought they could require PP to do anything in response. Even if the creator of "My New Army Builder" wrote a post saying "Buy my new Army Builder here:" the infringer is the creator of the program, not the operator of the forum. Surely it is the responsibility of the infringer to come into compliance. Perhaps the forum has a duty to co-operate with Lone Wolf's attempts to enforce its mark, by deleting specified posts which advertise infringing products. Perhaps the owner of an advertising board would have a duty, if informed by a trade-mark owner, to remove a poster advertising an infringing work. But while Lone Wolf are arguing that people have conflated their first, strong demand and their second request for assistance in educating people that 'army builder' is not a generic term, I think they overlook the strong possibility that the first claim is just as (if not more) flawed, as it seems to indicate that PP themselves are infringing on Lone Wolf's trademark by 'permitting' the advertising of an infringing product, and I find that unlikely.