If someone attacks you with a knife, are you only allowed to use a knife to defend yourself, or can you pull your firearm and put them down with that? No one would say that a firearm is a 'disproportionate' response to a knife.
And that is because force is only disproportionate if it is (far) in excess of what is reasonably necessary to bring the aggression to a halt. A solid case can be made that, far from being disporportionate, the Israeli response has fallen far short of what they are entitled, and perhaps even obligated (to their citizenry) to exert.
If they're not doing everything necessary to stop the attacks, they're not doing enough.