While it's not clear from the article, if it can be shown that PH didn't act in a manner adequate to defend the plaintiff and an appeal was made to Visa to cens

While it's not clear from the article, if it can be shown that PH didn't act in a manner adequate to defend the plaintiff and an appeal was made to Visa to censure PH for not removing felonious material from their website -- material from which Visa themselves were making money -- then it stands to reason that Visa can be sued as a conspirator. I am not a lawyer but it might be against the law for Visa to have anything to do with the funding of child porn; if they were notified and didn't act sufficiently against PH I can see where there would be more than enough cause for a legal complaint.