It's just bad apples, honestly. I guess they were either being impatient with me for not knowing, or they were having a bad day or something.
When I'm in a dungeon, I try to pay attention to my surroundings and not run ahead of the tank; if anything I'm actually ensuring that I stay closer to the healer and other dps when we're taking care of the mobs. Learning as I go, more or less. Hence my confusion whenever such things happen. I never say anything in the party chat except for thanking everyone for the party, letting others know whether or not it's my first time running a dungeon, and overall just being cordial and respectful. I guess I'm just not used to people acting a certain way, especially in public spaces like MMO's :'D