Sure they had a right to revolt. Firstly, as has been pointed out, when enough people aren't happy, they have a right to do something about it.
Secondly, what is always downplayed be these arguments is the representation.
It was said that "Americans didn't really want representation." That's true for the Sons of Liberty and some other agitation groups, but for the broad masses this was an important distinction.
The men in London had spent a lot of money on the colonists' defense, and it is only fair that the colonists themselves should help pay. The taxpayers in Britain proper were still paying even higher taxes, even with the Stamp Act.
Think about it this way: You have no representation in DC. The President and the Senate are now hereditary, and the House of Representatives can only be manned by people from the District of Columbia.
On top of that, they have a state religion that isn't the same religion as 90% of the rest of the country.
They also send the army around, who often sneer at the rest of the country as being bumpkins and you are legally obliged to host young male soldiers who havent' seen a woman in months at your house with your family instead of them having a barracks or something.
Eventually, you're just asking for trouble, essentially. Them telling the rest of the nation to fight a war and then raise taxes was just a spark that made people resent the system; having soldiers use lethal force on an angry populace was raising the stakes; and then going in to active military combat against a few pissed off partisans was where they lost the colonies.
It's the same thing that happened in most of the British Colonies - they (naturally) had a system that heavily favoured Westminster, and when cracks in the system emerged they were completely inflexible and tried to kill everyone who opposed them. The Commonwealth countries of today agitated when there was a more flexable Government in London. The Canadians were able to get a Home Rule Bill, the Boers were able to sue for an early and rather just peace; and so on and so forth.
-TIG
Alis Volat Propriis; Tiocfaidh ár lá; Proletarier Aller Länder, Vereinigt Euch!