I think this is an English thing. That “widely trafficked forum” means to me that it is popular. If I wanted to imply they were a part of trafficking I would write “ar15 a popular forum for the trafficking of firearms” or something like that. Trafficked does imply the illegal part, but the way it’s written that makes no sense.

it may have simply been an opportunity for a better choice of words. in this case, i think they meant trafficked as in heavily visited.

I meant site traffic, yes. Thank you for clarifying.