You are confused because you missed a crucial distinction. The blame for black crime must ultimately lie with blacks. The blame for white people's attitudes about black crime lies with whoever influences those attitudes, i.e. the media (in very large part, though not completely). If some black youths kill a white man over $1 and are sentenced to probation and an anger management class, it's local news. Most Americans won't hear about it let alone get angry about it. Reverse the races and it's a national outrage.

Think of it like this. If you never left home, so that your only knowledge of the outside world came through your TV, and I as a media exec decide what is shown on TV, I can arrange it so that no news of black crime ever reaches you. I can also show you only reports of gruesome crimes committed by whites. You would then waddle away with the impression that blacks are the most pacifistic creatures ever to walk the earth while whites are just irredeemably venal. Who deserves blame for what in this scenario?