The point is that all the same arguments were brought up against the previous anti-apartheid movement (the one in South Africa) at the time, and today almost no one would argue that those sanctions (and boycotts and divestments) weren't justified. Least of all on the basis that they "hurt, not help" the oppressed population. So this objection to the same tactics now is unconvincing.
The difference is that Israel is not apartheid (obviously).
The Palestinians are a different country. In South Africa they are all one country so they have to work together.
In contrast with Palestinians it's a different country entirely, so when you prevent them from working, you have little effect on Israel at all, you just hurt the Palestinians.
Officially, the black areas of South Africa during apartheid were different countries too. It seems to be something we've forgotten because apartheid South Africa has few supporters these days and it was obvious they weren't really since they were completely dependent on white South Africa economically and politically.
> Officially, the black areas of South Africa during apartheid were different countries too.
Well, no. Some black areas in South Africa (and South West Africa under South Africa's occupation) were converted into notionally internally self-governing regions, but of the twenty (10 each in South and South West Africa), only 10 (4 in South Africa, 6 in South West Africa) were ever even nominally (that is, according to the South African government -- no other government recognized any of them) independent states, and, in any case, there were a lot of black areas in South (and South West) Africa that were not part of either these "homelands", whether the notionally independent ones are otherwise.
(Now, in 1970, all of the black people of South Africa, whether they lived in the "homelands" or not, were assigned citizenship in one of them and had their South African citizenship cancelled. But that doesn't mean that the "homelands" covered all the black areas.)
