What was it about Peter Abelard's ideas that got people so upset and caused so much arguing and controversy with him and then later people like Bernard of Clairvaux?
He's a very important thinker in that he basically founded scholasticism. He played a big part in the West and the Church embracing reason over blind faith, viewing the universe as something that should be understood logically, and also in turning Aristotle into the main intellectual authority.
But the opposition to him had less to do with his philosophical positions than with personal rivalries. The cathedral schools of France were a highly competitive environment, where teachers depended in their ability to attract and keep students. Some teachers would go to others' classes and heckle them, engage them in debates which could become vicious. Abelard was especially abrasive and especially good at putting down an opponent.