Another one of the greatest psyops in history is that being pro-mass migration is a "left-wing" thing.

It's not, actually.

(Mass-)Migration was and is a policy supported by industrialist, urbanite, liberal, right-wing C(r)apitalist elites.

Almost every major Communist or Socialist state in then World had (or still has) very strong immigration controls. And why wouldn't they? Every Socialist knows instinctively that immigration rates are strongly related to wages, employment and standards of living.