Didn't read all the other posts simply because we all have our versions of what a "bad player" is - it's naturally subjective, and it's okay that we all have different opinions on subjective material.

What I think are "bad" players? Players who...

... don't want to participate in a group-oriented strategy (e.g., "everyone stand over here!" *bad player stands over there instead for some reason*).

... think it's 100% the game's fault if they (or the group) can't win a battle/dungeon/etc.

... think that throwing a nearly entire full-party setup of ClassX-onry at a fight will win it, and ONLY ClassX NO EXCEPTIONS GRRRR *ANGRY FACE* (and yes, with the angry face indeed).

... are ignorant, and don't want to hear how he/she may better perform his/her role in a certain situation; especially if he/she is not performing well-enough fulfill such role.

As far as that player you interacted with... yeah D-bags come in all shapes and sizes, and whether they're "good players", "bad players", or w/e, they're still D-bags, and unfortunately their parents spawned them unto this earth and the internet has given them a false perception that people actually care what they have to say.