I don't think you've chosen your examples particularly well.

Abortion certainly can be a 'central' case of murder. Immagine aborting a fetus 10 minutes prior to when it would have been born. It can also be totally 'noncentral': the morning after pill. Abortions are a grey area of central-murder depending on the progress of neural devlopment of the fetus.

Affermative action really IS a central case of racism. It's bad for the same reason as segregation was bad, because it's not fair to judge people based on their race. The only difference is that it's not nearly AS bad. Segregation was brutal and oppressive, while affermative action doesn't really affect most peopel enough for them to notice.