Of course, it's unfair.
It"s intended to be unfair. The number of males in the African America per capita was much greater than in the European population. The design of the was remove those males from the voting potential of African America. No women could vote at the time. Creating felons had already been taken care of with the design (legislation), enforcement (police), and interpretation (court) of the law.
There is no real reason to prevent a person, who has completed his/her payment to society for a crime, from voting. What purpose does it serve?
The law is, and was, about constraing the vote of African America.
You are who you say you are. Your children are who you say you are.