I read QuirrellMort as being honestly horrified by Harry's conclusions from Hermione's death. My take is that Quirrell engineered the troll to kill Hermione in order to get Harry to become an agent of death, not of life. He thinks Harry could possibly find a way to achieve his goals and wants to prevent both Harry from getting Hermione back and from inventing "universal healthcare". There is also the side benefit of driving a wedge between Harry and Albus / Minerva.