Who said it? "The right to existence, . . . the right to a character and culture of their own, the right to development, . . . and equivalent rights, are exigencies of the rights of peoples dictated from nature."

Answer below.

It was Pope Pius XII, addressing Italian jurists on December 6, 1953: https://www.vatican.va/content/pius-xii/it/speeches/1953/documents/hf_p-xii_spe_19531206_giuristi-cattolici.html.

More from Pius on how the Church is truly international, respecting what is good in every nation's culture and not forcing one nation or region's culture upon another:

"[The missionary's] office does not demand that he transplant European civilization and culture, and no other, to foreign soil, there to take root and propagate itself. ..."

"His task in dealing with these peoples, who sometimes boast of a very old & highly developed culture of their own, is to teach & form them so that they are ready to accept willingly & in a practical manner the principles of Christian life and morality." http://www.vatican.va/content/pius-xii/en/encyclicals/documents/hf_p-xii_enc_02061951_evangelii-praecones.html