Who's to blame is political rhetoric. What is interesting for a social scientist like me, is the question what causes the problem. There must be a causal explanation and no, sorry, "they chose so" is not a causal explanation. The answer is probably far from being simple. It cannot be being a ethnic minority alone, because other minorities apparently don't have the same problem. But in that article the possiblity that it has to do with slavery and discrimination is ruled out prematurely. That at times when discrimination was stronger, these problems were not so apparent, doesn't mean it isn't the cause today, because the entire social climate in the US is different now.
As I said, it's a difficult problem, but simplifications don't help.