I can't imagine Finnigan just deciding on his own they might kill you because of your parents. Surely he got the idea from SOMEONE, Mr Rosier or perhaps his tutor?

The professors must have known that they were considered traitors. The Headmistress was teaching back when they went to school, wasn't she? And Professor Slughorn as well, and some of the others. It's a little surprising it never got around before this.

Professor Carrow hates you for loads of reasons, it's not just your parents. He hates you for being a Gryffindor, and for not treating half-bloods and muggleborns like dirt.

Is the Slytherin book interesting so far? I'm really curious about it now.