Well, there's no Constitutional argument to be had here. The authority of the USDA to inspect a farm that sells meat to consumers is pretty well-established and there's not a court in the nation that would find it to be unconstitutional. Is it ethical? I'd argue that of course it is, the government has a role in ensuring the safety of the food supply - but of course, that is a philosophical argument and I gather I'm arguing with someone who wants to eat meat free from any kind of government oversight, which is a bizarre hill to die on, but okay.

Here's a court document related to this case that lays down some facts: https://aglaw.psu.edu/wp-content/uploads/2021/06/USA-v.-Millers-Organic-Farm-Order-to-Show-Cause-6.7.21.pdf

I think it's significant that Millers entered into a consent decree, legally agreeing that the farm sold meat products that were subject to the USDA's authority to regulate and inspect, and despite warnings, continued to engage in practices that the court told them they couldn't do. I also note that Millers never applied for any kind of exemption (and at this point, having continued to ignore repeated warnings and court orders, I'm guessing if they did so now it'd be too late).