This isn't about H1B and other visas, which BTW, do NOT allow companies to simply hire foreign workers.
This is about cheap labor being bused in and housed from other EU member nations, taking the jobs of locals who are just as or more qualified. it's about government not putting the needs of it's on people first, which is illegal under this EU treaty. it's about A nation being governed by leaders not accountable to the people.
Here, H1B visa's are only allowed when a qualified person cannot be found within the local jurisdiction/state. You'd also be hard pressed to prove that they were being paid less than what the local job market demands as well. H1B visa's are mostly used for jobs pretty high up on the cooperate ladder.
It’s also about the exploitation of those poor people being used for cheap labor.