You can be anti-apartheid, whilst also disagreeing that a good solution is to start bombing shopping malls and railway stations.

Of course it is, it's the very definition. Obviously he's just trying to justify his stance, but you're still disregarding his argument which could be just as easily made by someone pro-apartheid or anti-apartheid since it's orthogonal.

Blowing up civilians is probably required at times, I don't know, but the exact border line where it moves from acceptable to unacceptable is a difficult one. Some people (justly) hold that it is always unacceptable and there is definitely nothing wrong with that stand. Others are more pragmatic and can accept that killing 10 civilians is preferable to having 10,000 slaves.

It's not an easy answer, don't dismiss it as an ad hominem.