I think it's a bit misleading to say that blacks are 4.1/7.5 times more likely than whites to have probation/parole violations, respectively. 

From the report, those figures are based on the numbers of probation/parole violations as a proportion of the *total* adult populations of each group. On the other hand, if you look at the numbers of violations as a proportion of the number of people in each group *already on probation/parole*, blacks are only 1.2/1.4 times more likely than whites to have probation/parole violations, respectively. 

Of course, this is reconciled by noting that the proportions of the black population on probation and parole are, respectively, 3.4 and 5.5 times the corresponding proportions in the white population. Whether this fact is symptomatic of systemic racism is debatable, but this article seems to suggest that the disproportionality is *because* blacks are significantly more likely to violate probation/parole than whites, which misrepresents the report.