Many of them had relatives here. These were business people, professionals, who could have contributed to our society and to our war effort. Even that quasi-illiterate tinpot dictator Trujillo welcomed Jews from Europe into the DR.
Trujillo had a thing about white immigration - he massacred a lot of blacks in an effort to cleanse the Dominican gene pool. Compared to Trujillo, FDR was the soul of moderation.