These are cows, not someone's wife or child. It's not a medical "treatment." The "yahoo farmers" (oh, the condescension) weren't treating human beings or even cows for cancer. Why bring up breast cancer - and presume that's what the poster referenced - when all we're talking about is inseminating cattle?
Farmers don't have the luxury of calling a veterinarian every time they need to treat their animals, by the way. Perhaps you should watch a few episodes of Dr. Pol.
Agreed; these are cows, not people. That being said, the law does currently proscribe practicing veterinary medicine without a license, and using ultrasound to determine whether a cow is pregnant or not is a medical diagnostic procedure.
After the first warning, these two should have been working to change the law, not simply thumbing their noses at it. What they did was tantamount to waving a red flag in front of a mad bull.