You said Israel is currently governed by ultranationalists engaged in genocide that need to be stopped.
Consider this question: What exactly needs to happen for Israel to "be stopped?" There's been recent polling showing that something like 80% of the population supports what's currently happening in Gaza and 2/3rds of the population oppose allowing ANY humanitarian aid in. Therefore removing Netanyahu and the current government is not sufficient - a new government would be voted in that will immediately continue where they left off.
Didn't say it was, and that's absolutely not where I'm going. There's a huge difference between dismantling the power of a geopolitical state in order to stop it from committing a genocide (which is what most people mean when they say "Israel doesn't have a right to exist") and the genocide of that state's people. Don't conflate the two
When the Nazi German state was dismantled following WWII, was that a genocide against the German people? Did the Third Reich have a right to exist?
Would trying Hitler and his leadership for crimes against humanity have been sufficient on its own? Of course not, the entire Nazi German state apparatus needed to be dismantled.