Frankfurt discusses the difference between bullshit and lies. Lying is a conscious act of deception, while BSing is distinguished by its indifference to how things really are. The liar, in order to lie, must know what he thinks is true, whereas the BSer doesn’t care what is true. So in a sense bullshit is a greater enemy of the truth than lies are.
Frankfurt says that the reason BS is so common is because people are convinced that they are obligated to have opinions on everything, and so they pretend to understand issues they know very little about.
He goes on to suggest that one source of the influence of bullshit in public discourse comes from an attitude that rejects a concern with objective reality in favor of being true to ourselves. “Convinced that reality has no inherent nature, which he might hope to identify as the truth about things, [the individual] devotes himself to being true to his own nature.” But what makes us think that our “true selves” are any more stable or determinate than facts about the world around us? It’s a good question, really.