What exactly is racist about it? And you can't isolate the sentence without placing it in context of his alleged remarks. There is no doubt that the number of blacks in jail far exceeds their percentage of the total population. Nor can you dispute that blacks use abortion to a much higher degree than other groups in our society.
I read the "learn to pick cotton" remark as the failure of blacks to obtain the requisite skills and education to get a job and earn a decent living. Instead, they are dependent upon big government, which is just another form of slavery.
The point is, he (allegedly) said black people abort their babies and are in jail BECAUSE they never learned to pick cotton.
There’s nothing more to be said than that to explain it’s racial overtones. You may interpret it as you have, but it’s also perfectly reasonable to interpret it as saying, “black people were too stupid to pick cotton, to earn a decent living for themselves, so now they turn to crime to do so and abort babies that cost too much”.
That’s another, perfectly valid interpretation of the phrase in question and it’s racist.