It is unclear how much of their rhetoric is malicious and how much is what they honestly think.
Even during the current sessions before the ICJ, each side listens to the same arguments and comes out with diametrically opposed interpretations and conclusions.
It should be obvious to anyone watching the sessions that the South African case was a large set of cherry-picked "evidence" that was stripped of all context. The Israeli side is showing that they were deliberately ignoring most of the facts, as well as every fact that contradicts their case.
Israel's lead lawyer is the expert who literally wrote the most definitive book on international law, Malcolm Shaw. He summarized how South Africa's case was distorted and malicious.
But the other side is dismissive:
The question is whether the ICJ jurists themselves are just as partisan as the two sides are.
The promise of the ICJ is to be as objective as possible and to evaluate the evidence honestly. This is where, in an ideal world, the lies should be exposed. Unfortunately, ICJ judges have been shown to generally follow the politics of their home country more than independent judgment.
This is more a referendum on the ICJ itself. If they rule for South Africa's case in any way, it will show that the ICJ itself has failed in its mission.