I believe intentionally breeding people for menial jobs was called either the Hindu caste system or slavery, depending on your location. Even stupid people get pissed off and don't like being used by other people.
I've seen Gattica but it's science fiction.
No one considers identical twins any less human beings because they are identical.
Or, are you saying it is ok to enslave twins?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13