openly of removing the nation of Israel off the face of the earth, and you could therefore relatively easily label their actions as genocidal

“Israel” is a national entity ruled over by a state - calling for the destruction of a classical liberal nation state (never mind a colonialist-settler project masquerading as one) isn’t genocide in any shape or form. You might as well argue that people calling for the abolition of the Apartheid-state were “calling for genocide.”

Legally, genocide is not a particularly fruitful term

Not everything is about legality - we all know who writes the laws and for whose benefit they are written.