Actually the biggest supporters of open immigration are democrats looking for fresh votes and the Chamber of Commerce looking for cheap labor. Sure there are communists in the mix too, but if you paid any attention to communist intelligence operatives their main target has never been open communists who are more or less useless idiots. Their main target has always been useful idiots who can be coopted. It wasn't the American communist party that sold the bomb secrets to Stalin. It was deep cover operatives who did it while the FBI and military intelligence guys were all out looking for communists.
So, if you want to go beat your head against the wall trying to figure someing out go try to figure that one out.
PS That is why the useless American communists are useful idiots. They distract our counterintelligence agents who are off looking at every member of the American communist party. Meanwhile one of their famous coups was the Walker spy ring who sold the Soviets our naval crytopgraphic codes. The Walkers were not communists. They just wanted to make a buck, it turned out.