And herein we see the problem of states :-)

But less flippantly: it's no more "might-makes-right" than the original theft/"sale" was, and is arguably less so, given that national museums tend to survive regime changes (usually for nakedly political reasons, such as the incoming regime lashing its legitimacy to the country's heritage).

And on the aesthetic side: all things being equal I, a mostly disinterested Westerner, would rather see artifacts in their regional and cultural contexts than in a dimly lit room in the British Museum.