Machlokes: A Mussar Shmuz
From the onset of Year One, Professor Severus Snape bears a deep-seated enmity toward Harry Potter. This is due to a Machlokes Snape had with Harry's father nearly twenty years previously; Harry himself has done absolutely nothing to deserve such animosity.
Upon further examination, this seems ridiculous! Snape lived a large portion of his life as a double agent for Dumbledore and risked his life on many occasions just to ensure that Harry remained alive, yet he hates Harry because of a few petty fights he had with his father when they were in school. Why couldn't Snape just grow up? Who cares what happened when he was at school decades ago?
We see the tremendous power of Machlokes. Machlokes causes people to take actions they would never take under normal circumstances, actions that go against their core beliefs and even actions that counteract what they had been working their entire lives to achieve.
How much, then, must we must all try our utmost to distance ourselves from Machlokes!