Thank you!

Harry is losing some of his grip on his morals, too. At the moment, while he's kind of uneasy about using a Memory Charm, he thinks that's better than what would happen to him if Snape found out.

Remember that it's his experience with Snape that has prejudiced him, too. He was willing to love Sirius on a few hours' acquaintance, but Snape has bullied him and tortured him for too long.