Is one of the reasons Quirrell set up those Occlumency lessons that Harry would discover for himself "how reproducible human thoughts were when you reset people back to the same initial conditions and exposed them to the same stimuli" - and thereby come to treat humans as simple machines that one can use like puppets? As a strategy to bring someone over to the Dark Side, that's brilliant.

Indeterminate at this point. (By which I mean, even if Eliezer didn't intend Quirrel to have those reasons, he could easily make Quirrel have had those reasons.)

The reasons given earlier are quite enough to justify the lessons: Quirrel doesn't want Harry to be easily scanned by either Snape or Dumbledore for obvious reasons, and once he threw his hat in the ring, a neutral third party was the only viable option - and such a neutral third party can only remain neutral by being Obliviated since anyone in the know about Voldemort is, eo ipso, a member of one faction or another.