Not really sure why it's sexist.
Not really any more sexist then asking who will be the best Secretary of Defense.
Granted, the role of Hostess isn't quite as important as the SecDef, but First Lady is a role within the government.
-----signature-----
Jesus saves, Allah protects, and Cthulhu thinks you'd make a nice sandwich
First comes smiles, then lies. Last is gunfire. -Roland Deschain, of Gilead