Bismillahi Al-Rahmani Al-Rahim

 Fanaticism
The following are a few things that Ibn Hòajr Al-Haytamī (Allah have mercy upon him) included in Al-Zawājir `An Iqtirāf Al-Kabā'ir, his encyclopedia of everything ever said to be an enormity. It seems appropriate to mention them, because some people have incredibly bad manners when it comes to 'protecting' others from all outside opinions.

Zealotry for other than Allah's religion
(The Reliance Of The Traveler, w52, entry 22)

This includes fanaticism to a madhhab, caprice, malice toward opponents in arguments and debates, contempt, and thinking little of others. These some of the things that ruin devotees and scholars, to say nothing of everyone else. Busying oneself by defaming people and mentioning their shortcomings is a part of natural disposition. When Satan makes one believe it is justified, one exceeds, sinking deeper into the mire: gladdened and assuming that one strives for the religion while it is nothing other than striving in following Satan without it being following the Companions or their successors (Allah be pleased with them all) for whom one is fanatical. If only he were to give attention to taking care of his self [nafs] and having the same character as the one for whom he is fanatical, it would be better for him and more appropriate from him!

And the presumption that one's fanaticism by cutting down other people and belittle them makes one endeared to the person for whom he is fanatical is a falsehood. If that person were alive he would not have fanaticism for himself and would pardon those who were insolent towards himand this is even more appropriate for those who follow him. Everyone who has fanaticism for an Imam and does not walk his path: that Imam will dispute him and will be one of those to reprimand him.
(Al-Zawajir `an iqtiraf al-kaba'ir, 1:85)

* * *
Following one's caprice and ignoring the truth
(The Reliance, 27)

Which includes being hasty and not verifying.
(Al-Zawajir `an iqtiraf al-kaba'ir, 85)

* * *
Not accepting the truth when it conflicts with one's own preference, or when it comes from someone one dislikes
(The Reliance, w52, entry 32)

* * *
Concealing Sacred Knowledge
(Ibid, 44)

* * *
Neglect that results in the loss of people such as Islamic scholars, or sarcasm towards them
(Ibid, 47)

May Allah remove all of these things from out hearts and protect us form them.

wa al-salamu `alaykum
--musa