No nothing is destroyed, it's all saved in Wiki. 
 It's just that the material doesn't fit the topic. Actually my very first published essay was a review of that Violence in America book (1970) that was listed.  As for POV: the labor union movement has treied to portray itself as a positive force in terms of working conditiions, wages, political voice for workers.  That gets overshadowed by stories of violence  most of which does not involve mainstream unions at all.