If there is a job available and there are two people available, a local and a visa holder, the job should go to the best person suited for the job.
If there is a job available and and there are unemployed locals with the skills for the job, the company should not be able to attract someone from overseas to fill the job.
If there are visa holders who have a job, but don't get their visa renewed because there are unemployed locals with he same skills, and then forcing the company to replace pilot a with pilot b because they are local, that goes too far for me.