It's official - stated by a Trademark Judge:
"In short, the record shows that there is only one Evil Empire in baseball and it is the New York Yankees," wrote the judges. "Accordingly, we find that [the Yankees] have a protectable trademark right in the term . . . as used in connection with baseball."
The article continues:
In fact, it was Boston Red Sox CEO Larry Lucchino who coined it back in 2002 after New York signed Jose Contreras out from underneath them.
Now from the mouth of a judge it's OK to hate the Yankees, LOL.