It's kind of futile to give an example of sanctions working to someone who clearly stated that they some times work.

That's quite accurate - instead of trying to state any reasoning that would be refutable your statement above doesn't guarantee anything while implying a lot - thus it's pretty unassailable by logic. The implication is rested on a very relaxed statement and will continue to imply even while counter examples are raised.

Actually, I made a very refutable statement:

> Successful sanctions are the exception.

To refute, you just need to look at all sanctions, and enumerate the successful ones, and show the proportion is at least half.[0]

If "all" sanctions is onerous, a decent sample (e.g. "sanctions in the last 30 years") would still have weight.

But simply giving an example of something that the claimant clearly agrees with - that's not even close to a refutation.

[0] Clearly one can disagree on what success means, but then nothing in society can yield to logic

Reduction of foreign military expenditure by Gorbachev, political settlement in South-West Africa/Namibia, and the eventual fall of the Soviet Union arguably did more to remove any remaining rationale of the segregated government.

In any case, sanctions/disinvestment caused many foreign companies to sell their South African divisions at a great discount to white industrialists. These industrialists in turn greatly benefited by opening up in the 90ies.