I don't know if any defense against the order would necessarily rely on the First Amendment, or if it does it might not be from the obvious angle. I'm tempted to say it should be overruled or reigned in a bit on procedural grounds for trying to enforce a court order on groups who are not party to the case in any way, shape, or form, including ordering around unspecified groups who don't even know about the order, but IDK if that's an allowable practice in law or not.

I wouldn't count on the whole thing getting much attention, though- since the website is just ignoring the court, the only ones who could fight it would be the ISPs and businesses who want to provide services to the website, none of whom are likely to dedicate the resources for a lawsuit when it's much easier to just comply.

On the other hand, a single judge's order doesn't generally set any real precedent unless it get appealed and reviewed by a higher-level court.