I really like how you've phrased this here — I think I'm going to end up borrowing aspects of your explanation to use myself. The person you're replying to in this thread seems too entrenched in their opinion to hear the point you're making here, but I not too infrequently find myself trying to explain the nuance of this phrase to people who are pro-palestinian liberation, but unsure about this particular slogan because they (quite reasonably) don't want to inadvertently respond to a genocide with pro-genocide.

I've usually had good success in explaining why "from the river to the sea" isn't inherently a pro-genocide slogan, but I feel like your explanation will help me to do this more effectively in future.