Imperialism is defensive when cooperation is structurally impossible.
But if cooperation is possible it is preferable.
Even then the goal is merely institutional development so that cooperation is possible.
Imperialism like violence is an amoral question.
Extraction is not. Predation is not. Parasitism is not.
There is a vast difference between teaching people reading, writing, arithmetic, accounting, property rights, and the common law, so that you can cooperate with them rather than either conquer or displace them, or parasitically using them. And since parasitism is a way of life in primitive cultures -which is why they are primitive – it is a very long and difficult lesson to teach them.
I don’t like imperialism. I don’t like empires at all. I do like cooperative production and trade.
Respect for others’ property today will mean others may at least attempt to respect your property tomorrow.
So I would have to separate cooperative imperialism from parasitic imperialism.
I just have no idea as yet how to guarantee the implementation of it except as containment and habituated exchange.