All discrimination in South Africa is by definition illegal unless stipulated for by government. This is constitutional law.
If you somehow got ahold of their arrest record (not their criminal record), and used that to discriminate against someone, that would be discriminating against someone for no valid reason.
so you are telling me, if you worked in HR, and you got a CV in of someone who finished their degree in 2016, you would not go out of your way to check if they took part in the fees must fall protests?
and you are telling me that not picking that CV ahead of someone who also studied at the same uni, at the same time, but has no arrest record would be discrimination?