The idea of "repatriating" artistic treasures taken by imperial powers sometimes involves simplifying history, focusing on only one injustice out of a history of many such.

Projecting modern standards of right and wrong back into the past is often misguided and simplistic. The principle that nations shouldn't try to defeat other nations and take their land is a modern advance in morality. We should campaign to uphold that principle against nations that violate it today.

In the past, though, just about every nation got its land by taking it from some other nation. Empires were generally created by subjugating other nations, and that surely includes Benin. That was not merely common practice, it was also considered acceptable. If we were to judge their past conduct by modern standards, we would condemn almost every nation.