I agree that the U.S. is more selfish and individualistic than even other capitalist countries. I agree that fewer people in the U.S. will respond positively to discussion than they would in other countries.
But some people will respond to it, while no one -- especially not hyper-individualists! -- will respond to variations on "fuck off." I'd rather engage with some people than with no people, because while the former may be a long shot, the latter is a guaranteed loss.
I genuinely don't get how anyone thinks "agree with everything I say immediately or fuck off" is going to accomplish anything. That is exactly the shit we laugh at small weirdo ultra sects for doing.