Nelson Mandela Close to Death

At the risk of sounding like I am justifying terrorism few revolutions are brought about bloodlessly and there is such a thing as just war.

You have to consider the what was going on at the time that Mandela was embracing violent revolution. The Apartheid regime showed no interest in negotiating and were using their military to suppress movements. By the time FW DeKlerk came to office they understood that the World was against them and that Apartheid was going to end either peacefully or violently.