@blublab123
Parasite usually has a bad relationship to their host. And usually dont just kill, but simply eat their host slowly until it eventually dies. If vampires are just slaughtering people, that isnt parasitic. But if they are keeping human blood farms, then that is parasitic in nature.
Parasites use their host for something benefocial to them, without returning anything beneficial to their host. In that reguard, it defenatly is parasitic, especially in MC's case where his true vampiric self is slowly eating away at his current human self.
I do find it interesting how both of them immediately jump to a "who is more in the moral right" argument without even knowing anything about the other. And then she use the "but there are bad humans too" argument. While she isn't wrong, she also isn't necessarily in the right either, given how she is speaking from an extreme minority position.
MC isn't right to call her out like that, but you can't fault him for doing it either, given his history. In addition, nothing as of yet has really shown him that this organization can be trusted, given that he was coerced into even going there, and the teacher isn't making it any better by constantly shitting on his every action like that either.