The author tries to make the point that blacks don't kill each other more than whites by arguing that blacks have a similar intra-race murder percentage as white people do. Meanwhile, the pinhead author completely ignores the total number of black people that other black people kill which is far, far higher than the total number of white people that other white people kill.
I hope that, for his sake, the author is being intentionally disingenuous because it's hard to imagine that he can be this stupid.
Yes, it's a classic case of lying with statistics. The frequency of white victims per white criminal is roughly comparable to the frequency of black victims per black criminal. That's not what's relevant here.
What's relevant to the question of whether blacks are disproportionately criminal is how many violent felons there are per 100K blacks vs. how many violent felons there are per 100K whites.
There are about 7 times as many whites as there are blacks in America (keeping Hispanics in a separate category), while the total number of violent felonies committed by both groups is about the same. That means that on average, blacks commit about 7x as many violent felonies as whites.