I think that Harry Frankfurt's thoughts on the perniciousness of bullshit are only becoming more salient. It seems to me that most of what passes(?) for discourse today is exactly what Frankfurt defines as bullshit. The essence of bullshit is a complete lack of concern with the truth or falsehood of statements being made. Bullshit is pernicious because
[s]omeone who lies and someone who tells the truth are playing on opposite sides of the game. Each responds to the facts as he understands them ... The bullshitter ignores these demands altogether. He does not reject the authority of the truth as the liar does, and oppose himslf to it. He pays no attention at all. By virtue of this, bullshit is a greater enemy of the truth than lies are. pp. 61-62
Some other gems from his essay On Bullshit:
It is just this lack of connection to a concern with the truth - this indifference with how things really are - that I regard as the essence of bullshit pp.33-34
Through excessive indulgence in [bullshitting], which involves making assertions without paying attention to anything except what it suits one to say, a person's normal habit of attending to the way things are may become attenuated or lost. p.61