Snape was a former Death Eater. He has the tattoo to proove it. There are too many people who won't forget that. So Snape has his work cut out for him.

But with all these magic solutions flying around, I think there is a genuine lack of communication between Dumbledore and Snape. I understand that Dumbledore is a hands-off kind of guy, but it wouldn't hurt for him to bag the magic and just talk to Snape about the possible consequences of his behavior. It might even help.

If Harry managed to save Snape's life during a battle, would Snape be grateful or would he resent Harry even more?