The guards (i.e. "Corrections Officers") won't be able to isolate him from the general population unless they put him in "the hole" for good. There is no way OJ would agree to that. Solitary confinement is its own kind of hell.
Prisons have a subculture which contains their own "government." Most of it is run by gangs that are divided among racial lines: Black gangs, Hispanic gangs, and White gangs.
Blacks and Hispanics are not minorities in prisons - in many cases they are majorities. Therefore, they have real power through numbers.
OJ will join the black gang and seek protection there. The guards will not be able to protect him 24/7 - and in reality the guards even deal with the gangs on the inside because they know they have real power and authority on the inside.
Guards could not prevent Jeffrey Dahmer from being killed either - and he was as high profile as you can get.
Why would OJ need to be separated? Even at 61 he's a very strong and fit man. Also I suspsect the black gangs would respect him. He won't be anyone's bitch. In fact he'll probably end up getting himself a white bitch.