Because it is not enough to simply stop carpet bombing of civilians. If you want to truly stop the violence, that involves eventually giving Palestinians full citizenship and civil rights on the same level as Jews instead of forcing them to live in ghettoes. That's how a free society works. Until Israel does that there can be no true peace. A separate Palestinian state is not an option because of all the illegal (under international law) Jewish settlements in the west bank making a border impossible to maintain.

Once again, apartheid is itself violence. That's what the slogan is rallying against