I'm not saying that exploiting immigrants for labor is necessarily good, but the free hand of the labor market doesn't usually achieve policy goals.
Farm labor is not very regulated, but until about 10 minutes ago it was flooded with cheap foreign labor which seriously distorted the pricing mechanism for labor. And, that distortion helped to paper over some serious money supply expansion, i.e. the foreign labor helped food not get as much more expensive over time as it otherwise would have. If we keep things steady for several years we will see the market stabilize and rebalance, albeit now at a higher level (due to past money supply expansion finally being realized in prices).
*Note that I don’t really support the haphazard way this has been done, and I’m not confident that things actually will be held steady given the political environment, I’m just stating what theoretically would happen if they were.