If you're saying something that people don't want to hear or accept, a significant proportion of them will reply with hostility. Not because they know the facts, or because they have researched it themselves, but because they're so psychologically involved in believing good news that they will oppose it with a reflex.
Some people have heard of The Method, which originally goes back to Stanislavski... he gave you six major pointers whereby you became that character and tried to fool your mind psychologically. That's it in a nutshell. Daniel Day Lewis is an example of somebody like that who stays in character between takes.