Jaderis,
I think he was nasty to Harry because he had to be in order to maintain his cover and Harry's resemblance to James only made it a little easier.
Nah, he hated Harry because he represented all of his resentments, disappointments & humiliations, he looked like James & was the son of someone he gretly desired but never "had". It was just that his hatred of Harry was at odds with his hatred of Voldemort, it's what made Snape interesting.
The failed occlumency lessons point to Snape's real hatred of Harry not being a cover up.
Mark
There are 10 kinds of people in this world; those that understand binary, & those that don't