If the message (1) is genuine; and (2) mentions only people that participated in the lawsuit, I think that is pretty good prima facie evidence that the idea is retaliation. There is no other apparent reason to refuse to deal with the free-lancers. Whether it is legal depends on what the law of New York says. In the State of California, all employment contracts are presumed to be at-will, so that absent an agreement to the contrary, any employee can be terminated at any time, for any reason. But there is an exception when the employee is terminated for a reason "contravening public policy," e.g. for being a minority or for reporting illegal conduct to a superior or to legal authorities.

So if this happened in California, and the free-lancers filed a second lawsuit, it would raise two novel issues:

(1) Does it contravene public policy to retaliate against people for exercising their constitutional right to petition for redress of grievances? (I suspect it does), and

(2) Can the rule against terminating employees in contravention of policy be extended to independant contractors, like freelance journalists (this is dicier)? New York law is generally a bit more conservative than California law, but generally similar principles tend to apply.