African-Americans, whether dead or alive, must be allowed to vote as many times as possible to make up for the White Man having kept them without the voting franchise during the 400 years of American Slavery.
And that goes double because many slaves were women, and the franchise was withheld from them for even longer by evil White Men, who also sexually harassed them.
The rationale for allowing illegal aliens to vote is just as good! In fact, due to the rich Latin-American literary tradition so rich in imagery and allegory, it is perfectly OK for people like the Sanchez Sisters to make up entire multi-generational Latino families. Dead Mexicans have feelings, too. Even imaginary dead Mexicans.