What is left when all other options are exhausted?
The American War of Independence, French Revolution and English Civil War were acts of terrorism.
Were those acts justified? Not if you're the ones who were initially holding the power.
The french revolution was terrible and made every single person in france worse off. It is the exact evidence that shows that even in a revolution restraint is still needed.
Calling the American Revolution terrorism, in the modern sense, is a stretch. It was a war waged primarily between soldiers and materiel with the goal of ending the enemy's ability to wage war.
Systematic use of terror as a policy to induce fear in the general public to push them to coerce their government's policy was not widely used.