The dispensing with niceness probably springs in large part from an extreme rejection of the ad hominem fallacy and of emotionally-based reasoning.
Another part is that the norm ‘be nice’ can be used to mean ends far more effectively than crude rudeness. Rejecting the norm and then actually being nice (for reasons along the lines of your 9) tends to be a lot, well, nicer.
Another part is that the norm ‘be nice’ can be used to mean ends far more effectively than crude rudeness. Rejecting the norm and then actually being nice (for reasons along the lines of your 9) tends to be a lot, well, nicer.