Arrogance, willful ignorance, bad manners and cluelessness are not nice qualities.
Arrogance is, for example, presuming that after being so wrong about our religious beliefs we do not need to seriously re-examine our beliefs regarding the nature of god, 'holy books' and science that have been so wharped by our exposure to a cult.
Willful ignorance is refusing to inform oneself adequately when one has deficiencies in ones knowledge pointed out.
Bad manners is not conceeding error when one commits error, not giving credit where credit is due.
Cluelessness is wondering why people get annoyed when one displays one or more of the above qualities.
If you observe 'un-nice discussions' they often feature ex-cultists still clinging to cultic preconceptions and assumptions about the world being offended at the very idea they might not be adequately informed about a subject to be able to competently pass judgement, refusing to go and do anything about their lack of knowledge, not admitting they didn't know things or saying they were wrong when they were, and then being surprised at the reaction they provoke.
Obviously sometimes those who are more knowledgeable (and it is mostly about knowledge, not about intelligence) are irracable, caustic, unreasonable etc., without any real reason. Sometimes they are just pushed to it by the above described behaviour. People pretending to have a discussion when they are just repeating the preconceptions they started with that no facts will change are annoying.
Ego can have as much to do with the 'I'm not adequately informed about this subject but am going to pontificate anyway' crew as with the 'intellectual' crew.
People should be free to be warm and fuzzy as they like, but being warm and fuzzy in a serious discussion (on a discussion board) and being bruised by the reaction is a result of their unrealistic expectations. Warm and fuzzy works on warm and fuzzy threads. Proper discussion need mutual respect, but that is a two way street; the aforementioned behaviour is not respectful.