No surprise there. I estimate playing WoW is more addictive and harmful to your productivity than smoking marijuana, and certainly you wouldn't mention the latter to a prospective employer. "Hate" is going a little too far though - probably the manager in question had a bad experience in the past. I doubt if you were a productive employee and you mentioned you play WoW if they would start hating you.
I suspect that WoW can be conducive to creativity, but for hard-core players this is often focused entirely on goals in-game. So in the case of hard-core players, the chances are that an employer will only lose out from decreased productivity. (Lack of sleep.)
Contrast this with interests in music, art, or sports, where employers can often stand to gain indirectly from even an employee's avid participation. Sometimes they gain directly, as in Shigeru Miyamoto.
