Reminder: Oh, Won't You Please Shut Up? (2011)

No, absolutely not. Even if you tell the whole truth as you know it, it can still get you into trouble. Maybe they have another eyewitness that remembers things differently than you do. Maybe they have an eyewitness whose account agrees with yours, but the LEOs themselves misunderstood or misheard or forgot something. The police are going to think you lied. Maybe you just honestly misremembered something. Nope, that's a "lie".

There are so many ways that you telling the truth can hurt you, and basically no ways in which talking can help you, that it's not worth the risk. Law enforcement does provide a useful benefit to society in general, but there is zero reward for helping the cops, and a lot of risk that you could land yourself in hot water for something that seems completely innocuous.

In the specific example from the blog post, there's no reason to lie--taking that call was not illegal, so there's no reason to lie.

The psychology of the situation is not to your advantage. The LEOs are trying to get you to lie. They know how to do this. I'm not saying you're powerless to withstand them, but the example in the blog post is just an example. They can and will use much more sophisticated tactics to catch you in a lie if they think it will help them.

And even in this example, what if you do tell the truth, and say you did talk to them about it? Then they're going to ask what you talked about with your friend, and maybe you don't quite remember it exactly how they do. That's "lying" in their book. It also opens you up to further questioning in general, and just when you're feeling comfortable talking to you, they'll ask you something somewhat ambiguous that causes you to lie, even unintentionally.

It's just not worth it. When law enforcement comes knocking with questions, they are not there to help you. At absolute best, it's a neutral encounter, but it's very easy for it to go against your best interests.

   One should understand that the Justice Department did not simply find 
   indirect evidence of unintentionally racist practices which harm black 
   people, but "discriminatory intent”—that is to say willful racism aimed to 
   generate cash. Justice in Ferguson is not a matter of "racism without 
   racists," but racism with racists so secure, so proud, so brazen that they 
   used their government emails to flaunt it. [1]

[2] http://www.nytimes.com/interactive/2015/03/04/us/ferguson-po...

Why is it worst by being likely true? It's probably not a good idea to immediately invoke the Fifth on a routine traffic stop, for instance, for exactly that reason. (It wouldn't cause them to arrest you, sure, but they'd look a lot harder for reasons to cite you that would otherwise "not be worth it".)

"Sir, do you know how fast you were going?"

Presumably both "yes" and "no" would be bad. (The former is obvious, and the latter could mean you're not paying sufficient attention, etc.) So, do you just stare at them in silence? Do you say something like, "I'd rather not answer," which while accurate, sure sounds like "yes". (At the very least, there goes your chance of a warning instead of a ticket...)[1]

I agree with serve_yay that many of these situations start off seeming innocuous, and staying silent is easier said than done.

Another example is the cops canvasing the area of a crime, looking for info. Do you just refuse to speak to them without a lawyer, even though you had nothing to do with it? It's certainly possible (albeit unlikely) that they actually have you as a suspect and are trying to trick you into some sort of false statement. (Or a statement that appears to be false because it conflicts with other evidence, even if it's true!) But in the vast majority of cases it'll be exactly what it seems. Or say you actually witnessed a crime. Or were the victim! Still lawyer up before talking to the cops? It appears the safest thing is, yes, always get a lawyer. But at some point on the spectrum, does the cost and inconvenience outweigh the insurance factor of doing so?

[1] I've only been in that situation a couple times, but I've tried my best to answer politely without saying anything material. One way to do that is to answer questions with questions. "Do you know how fast you were going?" "How fast was I going, Sir?"

"But he obviously didn't mean that!" Then why the extreme repetition of "never"?