Fun fact: you can be against (big) employers skewing the market by getting away with abusing migrant workers without blaming the workers for fleeing even worse conditions.
In general, immigration (yes, including mass immigration)is a huge cultural and economic boon to any country with proper infrastructure to handle the transition. The problem is that corrupt politicians are negligent in enabling that infrastructure AND letting unscrupulous corporations get away with semi-slavery, not that the exploited workers are in the country in the first place.