Don’t limit it to just illegitimacy. The underlying situation is the step before illegitimacy, the destructive advocacy of sex outside of marriage, which is part and parcel to leftist ideology. “Free love” and that children must be raised by “the state”.
1) Sex outside of marriage works off the assumption that the purpose of sex is pleasure instead of procreation, which has the same inherent flaw as assuming that the purpose of eating is pleasure, not sustenance.
2) Since the purpose is not procreation, avoidance of pregnancy becomes important. For SD blacks this often takes the form of long term birth control, which takes away six month-long blocks of fertility from the front end of the about 20 year window of time optimal for having children.
3) Those who do not use condoms as birth control and have a number of different sex partners are far more likely to develop venereal diseases (including the now resurgent, antibiotic resistant gonorrhea). And several of these can frequently cause sterility in those infected, as well as severe and lethal birth defects. (Also common among those who use hard drugs, which cause a significant number of miscarriages and birth defects.)
4) Those who do get pregnant often have abortions, with all the associated negative consequences. Among SD blacks this is particularly common, with about 30,000 abortions a year in NYC alone. Insanely high, in that there are only about 2.1 million blacks in NYC.
5) Only then does the full impact of the effects of illegitimacy take its toll. With illegitimacy at 70% for live births, the majority of black children are in “survival” mode. And *only these* create such statistics like one in every four teen and young adult black males either being in prison, or on parole or probation.
Blacks are the canary in the coal mine. Whites are headed in the same direction. That's been the Fabian Socialist ( Marxist ) plan for more than 100 years.
And...Of all the many weapons directed at our nation's’ freedom, schooling ( Pre-K through graduate school) is the Progressive Marxist's most important and powerful.