I think this is a rationalization. Humans are always tempted to look up to power, and what's more powerful than an empire? It goes unquestioned that we should respect the Roman empire, for instance, and you pretty often see an argument for the Mongolian empire. But these days, we know that violence is bad so we have to find other reasons to justify our feelings. So we talk about the "peace" they established after all the war. But is the cost really worth it? How many people not attacked by bandits do you need to justify an innocent murdered by raiding soldiers? Never mind that even the "peace" is often sustained through oppression. The Romans didn't invent crucifixion for Jesus, it's something they did. Never mind that the empire never lasts, and plants seeds of the next dozen wars as it falls, watered with yet more blood.

Ask yourself: if you honestly intended to create peace, would a century or more (in the case of Rome) of bloody conquest actually be the optimal plan? I would say no. An actual plan for peace through strength looks more like NATO than Rome.

Any good an empire builder does is accidental. Whatever they tell you or even themselves, they do it for glory and power, and their actions are optimized for that over any actual benefits. They were not nobler than the conquerors and colonizers were rightfully decry today.