assimilationist (n.)

"one who advocates racial or ethnic integration," 1900, originally in reference to Hawaii and possessions obtained by the U.S. in the war against Spain; later with reference to Jews in European nations; see assimilation + -ist. In Portuguese, assimilado (literally "assimilated," past participle of assimilar) was used as a noun of natives of the Portuguese colonies in Africa who were admitted to equal rights and citizenship.