Ever try setting ground rules before diving into the politics of a story? Like, agree that no one's calling anyone a fascist just for seeing the surveillance state in their own way. When we talked about "1984", we said upfront that Big Brother could mean different things to different people. It helped us focus on the text, not our personal triggers. Also, maybe take a break when voices get loud and come back to what the author actually wrote.
Start by agreeing that all views are okay if they come from the book. It stops fights from getting personal and keeps things on track. We tried this and it worked well.