This seems to be clearly an ethical question to me, and the field of ethics is far from scientific. What kind of answer are you looking for?

My system of ethics would suggest that developed nations are morally obligated to help poorer nations (at least in so far as significant human suffering is caused by limited resources), and that this is the only relevant factor. So help disadvantaged peoples yes, but the cause (imperialism or otherwise) is irrelevant in determining the need.

If you would like a different answer, I can surely construct an argument pointing in the direction you prefer.