They lie about big things and little things. They lie to indulge their weaknesses, such as pride or vanity. In the most extreme situations these liars are trying to avoid pain or confusion that would overwhelm them and so they lie to protect themselves.
But others lie for money. They lie out of greed, and to advance their career. They lie for small professional triumphs over other people that will advance their standing, a permanent game of one-upmanship which they will always win because all they have to do is lie. To fight them we need to keep telling the truth to the best of our ability and refuse to accept the lies that are designed to harm us.
From a Bloggingheads video, May 12, 2008:
Megan McArdle: First of all, I hesitate to get around and start grotting around in markets unless I'm really really sure what I'm doing. I don't really see a way to fix this problem with some kind of government intervention. And second part problem is I'm leery how paternalistic it is for me to say, like, look, I'm obsessed with, you know, having a healthy green-filled diet and you must share that obsession and if you don't choose to share that obsession, if you choose fast food, I'm going to take it away from you because I know what's best.
Raj Patel, author of Stuffed and Starved: How do you feel about a tobacco tax?
McArdle: I'm against it for the same reason. People know that smoking is a cancer and if they choose to smoke anyway it's not my job to tell them not to do that.
Patel: Okay. Despite the fact that tobacco is addictive--or nicotine is.
McArdle: Well, yeah, I smoked and, like, quitting wasn't that-I mean, like, I smoked a lot, like a pack and a half a day for eight years, and quitting wasn't pleasant but it also wasn't impossible. You know, it's not something that you can't choose to do.
Patel: Oh sure, I went through similar pain and I had a hell of a time quitting, and in fact there are days when I still am dying for a cigarette even though I haven't had one in years. I'm sympathetic about it.
McArdle: I actually think that tobacco is kind of different than food in that going cold turkey is a lot easier than (unintelligible).
Patel: [laughs] I think so but the reason I raise the example of tobacco is because of a finding that just came out of (unintellligible) Medicine that draws on some of what you're saying--and by the way I agree with a great deal of what you're saying but there is a public health issue here. [re: obesity] Particularly in the United States. You're right in that you're not seeing people whose bellies are distended from hunger in the United States but you are seeing people whose bellies are distended, and that's because of over-nutrition and over-consumption and it's already started to catch up with us.
Megan McArdle smoking at the beach, May 29, 2009.

They have no idea how tired we all are of lies. We've begged them to stop but they're making too much money. They'll keep lying even when their lies become common knowledge. They'll keep lying until it destroys them. It's almost painful to watch.
Almost.