American morality...
https://en.wikipedia.org/wiki/Ankhhaf_%28sculpture%29
Along with a host of other artifacts in other western museums. You cannot judge the morality of the time by modern-day standards. Without such activities the rosetta stone would not have been deciphered, just to take one example.
Now whether such items should now be returned is a different argument. But one thing is clear - if one item must be returned - they all should. So all countries should be judged by the same standards - not just the UK.