The British Empire may have been materially a net good, but (as Benedict Anderson points out) it was doomed the day it embraced Macaulay's plan of cultural exterminationism through education.

"Independence movements triggered by liberalism" is a better way to put it than "independence movements", but it's not as accurate as "independence movements triggered by the combination of something involving the creation of an elite class educated in European things, often actually in Europe (or America), and later the Cold War scramble for puppet states between the two superpowers, hence their agreement on the issue of decolonization and probably Washington's shafting of Britain in Suez." Where do you think Pol Pot got his Marxism from? Certainly not Cambodia, and not even the USSR (the Khmer Rouge was a Western ally for a while) -- he got it in Paris, the center of the relevant empire.

(To take the Benedict Anderson hypothesis further, onto very speculative and shaky ground: could it be that decolonization arose out of the same impulse as Italy's misadventures in colonialism? In Italy's time, any serious nation had an empire; after WW2, any serious nation had its own state, except 'nation-states' couldn't exist because of pre-existing attachment to administrative boundaries among the elite, those boundaries having shaped their life far more in practical terms than native culture or ethnic identification. Also legibility reasons that Anderson doesn't mention AFAIK: precisely named and delineated boundaries that aren't accurate will be preferred over accurate boundaries that have yet to be drawn, because 1) the former is much more practically knowable and able to be acted upon by an organization than the latter, 2) the former are available and the latter aren't. Compare the use of states in America.)

Assuming for a moment that's what actually happened, when in history do you locate that event?