Rants about people using wrong definition of casual - writes a small essay proving he doesn't know what he's talking about. The world we live in....
Fyi, Having the liberty to engage with the game for the amount of time of your choosing - that's what it means to be a casual player, i.e. doing something irregularly.
If he has has 15 minutes to do some quests today - it's fine. If he doesn't want to do any - it's fine. If he suddenly has 3 hours to do quests and get some token currency on Monday - that does not make him a hardcore grinder trying to mask him being bad. Method and co. are anything but casual. Sure, new raid comes out and you can get insane amounts of ilvl/hour compared to any "bad"(in your words) player. Do you take into consideration the amount of time that has been spent getting to that point in time?