The fans of New York City FC, the soccer team that has never played a game, were under attack.

As they took their seats at January’s MLS SuperDraft, the abuse came from all sides. There were chants of “De-rek Je-ter” and a rendition of “Take Me Out to the Ball Game,” to make light of NYCFC’s rented home at Yankee Stadium. The purple-clad fans of Orlando City SC, Major League Soccer’s other new expansion franchise, bombarded them with “Where’s Frank Lam-pard,” referencing the star midfielder who will be noticeably and controversially...