Respectfully, if you refer to advocating black inmates take revenge on this pathetic little coward who murdered those who WELCOMED him among them according to the Messiah's admonishments concerning hospitality to strangers, I very much understand his 'sentiments'.  The Creator has promised to punish the unrepentant according to their deeds.  May Roof be murdered nine times after arriving in hell, and then shunned as a pariah therein for eternity--just as his victims were maltreated as if they were less than human all their lives under Jim Crow terror and tyranny, and thereafter had to watch helplessly as their youth were gunned down by both criminals and the cops who were supposed to protect them, until finally being murdered themselves.

Were it up to me, Roof would be stripped naked, plastered with hog-slop, kneecapped then thrown into a pit full of starving pigs.  And I say this knowing that to torture mortals is hara'am (Islamically unlawful).  Lannatullahi alayhi alf mura'at.