^Yeah, you can't blame him for that, especially if you also believe in the Snape loved Lily theory; not sure if I do though:/. I think that Snape is still good though, and might be helpful to Harry in his own bitter nasty way; he might even protect him from Voldemort if the time comes, maybe dying doing so(though I obviously don't want him to die). I know it seems a bit far-fetched, but the whole scene where Snape is fleeing from the school after killing Dumbledore and Harry is chasing him made me think. It seemed that Snape's telling Harry that he would be blocked again and again till he learned how to close his mind seemed almost like a lesson to me more than anything. Maybe it's just me wanting Snape to be good and to help Harry vanquish Voldemort, but that is what I think.