excluding polish immigrants

I think you’re confused. Prussia had annexed regions of Poland in the 18th century. The Poles in question were born there. They weren’t immigrants, just as Native Americans and Hawaiians are not immigrants.

“Left” you know the left that supported Germany’s colonial efforts

Yes, the “left” that supported organized labor and opposed capital. Which was the original goal of leftism. In Germany, the left was led by August Bebel who was described as a “model worker’s leader” by none other than Vladimir Lenin.

Anti-colonialism is a relatively new project for leftists. Old school leftists, including Marx, defended colonialism as a necessary step from feudalism to communism. Marx himself described the colonization of India as a “tool of history” in ending the “Oriental despotism” of the caste system and other “traditional rules”:

we must not forget that these idyllic village-communities, inoffensive though they may appear, had always been the solid foundation of Oriental despotism, that they restrained the human mind within the smallest possible compass, making it the unresisting tool of superstition, enslaving it beneath traditional rules, depriving it of all grandeur and historical energies. We must not forget the barbarian egotism which, concentrating on some miserable patch of land, had quietly witnessed the ruin of empires, the perpetration of unspeakable cruelties, the massacre of the population of large towns, with no other consideration bestowed upon them than on natural events, itself the helpless prey of any aggressor who deigned to notice it at all. We must not forget that this undignified, stagnatory, and vegetative life, that this passive sort of existence evoked on the other part, in contradistinction, wild, aimless, unbounded forces of destruction and rendered murder itself a religious rite in Hindostan. We must not forget that these little communities were contaminated by distinctions of caste and by slavery, that they subjugated man to external circumstances instead of elevating man the sovereign of circumstances, that they transformed a self-developing social state into never changing natural destiny, and thus brought about a brutalizing worship of nature, exhibiting its degradation in the fact that man, the sovereign of nature, fell down on his knees in adoration of Kanuman, the monkey, and Sabbala, the cow.

England, it is true, in causing a social revolution in Hindostan, was actuated only by the vilest interests, and was stupid in her manner of enforcing them. But that is not the question. The question is, can mankind fulfil its destiny without a fundamental revolution in the social state of Asia? If not, whatever may have been the crimes of England she was the unconscious tool of history in bringing about that revolution.