The only people who think From The River To The Sea is genocidal either learned everything they think they know about Palestine in the last 2 months (and learned it by uncritically parroting media narratives) or is engaging in cynical PR for the genocide itself. It has no basis in reality, so the only way to learn this anti-fact is the aforementioned ways. It requires an aversion to reading anything about the recent history of Palestine, in fact. Say, the last 75-100 years.

Liberal white supremacy means the white supremacy that is acceptable to and promoted by liberals. They might reject the KKK aesthetic but are more than happy to dehumanize the Palestinian population and revert to post-9/11 islamophobia the moment their masters say it's okay. The kind that tut-tuts the victims of racialized settler-colonial apartheid while providing full cover for the colonizers.

People often think, "how could anyone have stood by during American slavery, or the genocide of indigenous Americans, or the Nazis?". The answer is right in front of you: all of these liberals braying for Palestinian blood, bombing hospitals, and trying to punish just about the only voice in Congress pushing back on it.