That's advice if taken literally is horrible. Never talk to the cops if accused of a SERIOUS crime, always get some sort of legal council. If however you get pulled over for running a stop sign or some other traffic violation/small offense and you know the cop saw you, don't insult their intelligence. Judge the situation I've gotten out of every traffic ticket by being polite and honest. I'll usually try and apologize as soon as the cop walks over "i'm sorry officer i don't know what i was thinking going that fast" i've caught cops off guard saying stuff like that, they will usually reply "uh so you know why i pulled you over" a simple "yes" and an ashamed look will work wonders. Also use your judgment, if the weather is bad always have your license and paperwork ready before the cop walks over, "I know you're just doing your job i didnt wanna make you wait in the rain" has gotten me out of a few speeding tickets too. ;)
As stated above though, if you're accused of something serious just keep your mouth shut.
The difference is, a trafic cop doesn't want to arrest you. They don't want to book anyone, but their boss told them to go balance the books by fleecing drivers. If you make their job easier, they might let you off with a warning.
A cop who's investigating a real crime wants to get a conviction. And they aren't in a position to do plea bargaining (like a traffic cop), that's the DA's job (then the judge's, if it gets that far). It's not a terrible idea to negotiate with the DA and judge, but you need a lawyer to help you do it.
If it's possible you may be on the hook for something more serious than a traffic ticket, clam up; your implied admission of having done anything in traffic can harm you.
As stated above though, if you're accused of something serious just keep your mouth shut.