Mandela was a much a terrorist as Arafat, or Menachem Begin, who didn't murder anyone personally - but headed a terrorist organization.
The war in SWA and Angola involving the SADF wasn't about "decolonization" - but simply about spreading Communism (Dictatorships) across Southern Africa - so as to forcefully replace democratic governments with authoritarian systems. Whilst making use of "rightfully" propagating, that Apartheid aka the RSA or the Rhodesian DEMOCRATIC governments are only elected by Whites.
As such wrongfully/falsely discrediting Democratic White-African governments to be Colonialists.
Apartheid was a racist political system/ideology, and had nothing to do with Colonialism. Neither did Rhodesia nor the RSA possess any Colonies, unlike e.g. Portugal, the UK, France or the USA.