There are levels to this. The term used by diplomats and leaders is Proportionality.
Its already accepted that non violent means that nevertheless still negatively impact civilians are appropriate measures to apply political pressure. That's what economic sanctions are. I don't see how that can be considered acceptable yet cutting off digital communications is a bridge too far. I consider economic sanctions more severe than blocking the Russians from the global internet. One means you lose access to information. The other means your economy may collapse and you might not be able to afford food.
As for the 9/11 attacks, they were deliberate attacks on civilian targets which are traditionally considered war crimes when carried out by state actors and terrorist attacks when not. They are definitely far worse than softer measures like sanctions and not directly comparable.
And there is nothing arguable about it. They definitely backfired. Bin Laden did not hide his intentions or feelings. In fact he wrote extensively and publicly on it. He expected that the American public, who were broadly ignorant to US foreign policy at the time would empathize with him and blame their government. The opposite happened.