Why it's sometimes a good idea to use a negative tone against people who agree with your political opinions

The other day (or was it today?) my twitter peep T.S. Christian was writing about how she doesn't understand the tone argument (i.e. the argument frequently made about activist postings--that the tone is too controversial or strident): after all, the tone doesn't invalidate the content.

And I was thinking, you know, this is a common feeling in the activi…