I agree that casual and hardcore shouldn't automatically designate someones skill level. I disagree about his qualifications though. I think the hardcore players are the ones who spend almost every waking moment on the game. Just woke up: log in, just got off work: log in, should be going to bed because work is in 5 hours: "Nah I can call in sick if I'm too tired"
Basically think the ones that let the game interfere with their real lives are the only ones I would classify as hardcore.