Yeah, the individual rights of a car or RV owner not to be searched without warrant agains the welfare of millions of Californian's depending in their agricultural livelihood.
And people, there is such thing as "motor vehicle exception", and that includes RVs and trailers (being pulled by semis) first established by the Supreme Court in 1925 that motor vehicles can be subject to warrantless search. You in effect impliedly waived your rights to be searched without warrant upon purchase of the vehicle.
There were already so many decided jurisprudence on the matter.
And if I happened to be the inspector, I would have given the OP 3 options, submit to inspection, turn around or be detained on the border until they can get back into their senses on what important to them. If they act belligerent, I would also call the nearest LEO to make an arrest or impose my duties to make the inspection.