I agree with most of what you say, but I'm not so sure about the last two. As others have pointed out, there are many, many cases where the primary suspect of a crime is never prosecuted. Given a choice, prosecutors will usually choose "easy" cases. So an alternate explanation for America's high prison population and incredibly high black prison population is that * more criminals are prosecuted and convicted in America, and * jurors are biased and black criminals are therefore easier to convict; and/or prosecutors are biased and therefore prosecute more black criminals.

Now, since I don't think it's actually optimal for everyone who ever breaks a law to be punished, I have no problem saying, for example, "More criminals are prosecuted and convicted here, and that's too bad."