Why would the value of those plummet? Wouldnt the opposite happen? Did insurance prices fall, did insurance stock prices fall, when the government mandated insurance purchases? Do college prices fall when easy access to loans become more available? I dont follow how a free subsidy would lead to less of a crop? Do corn subsidies lead to less corn? The government would be paying rice producers for all the rice people choose to consume. The loser in that scenario is the tax payer who pays a lot and doesnt eat rice.

If anything, the argument against it would be picking and choosing industry winners: pistachio, avocado, cheese, meat markets would find it unfair.