Yes, people can indeed hate anything they want to hate. They can hate an idea, for instance, whether or not they think it's about something "real" or is in any way realistic.

If they do hate it, you'll see them react aggressively anytime it comes up in conversation, and they won't be able to ignore it, but will immediately attack it, and that's the point Jack is making. The attack is inspired by their deep hostility, and deep hostility is hatred.