If there were no illegal immigrants performing these "dirty jobs", then the pay for doing that work would necessarily increase to the level required for someone to take that job.

Having the pay increase to the required level would - of course - increase the cost of that product or service.

I submit that many/most of those who support illegal immigrants working these "dirty jobs" are more driven by the lower cost of fresh fruit & vegetables, rather than any particular interest in "social justice"...