1. Being as there are bad cops out there although we know the majority are probably good and being as we can't, by visual inspection, tell the good cops from the bad cops, and
2. Being as the cops can, and do, lie to you but woe be unto you if you lie to them, and
3. Being as every attorney I've ever heard say anything on the subject has said the same thing:
Don't talk to the police!!
Be polite, yes. Be courteous, yes. Keep your cool even when the cop starts screaming and spraying spittle in your face, yes. But don't talk to the police.
This Primus cop in the last page or so is giving dangerous advice--and he knows it. He's already been thoroughly refuted in previous threads. And, yet he pretends like those refutations never occurred.
He's great at giving examples of how talking to a cop can help sort things out and avoid arrest, but he carefully omits that the talker is rolling the dice on whether the cop is just looking for something to add to an arrest he already intends to make.
Primus also skips over Prof. Duane's point that police, if they have contradictory evidence, can use it to paint the talker as a liar, even if he isn't lying.
And, then there's the whole bit about phrasing something the wrong way when under stress or upset.
Here's the story of a guy who talked to police. His car was trashed when a moose walked in front of him. The cop spent a great deal of time and energy trying to pin a DUI on him (the victim). Check out what happened when the driver incautiously remarked, after repeated pestering, that he had a glass of wine with supper the night before.
http://www.lewrockwell.com/2013/12/eric-peters/what-are-they-good-for/
Flat out, Primus is no friend of freedom. Not when it took hundreds of years, torture, burnings, dispossession, imprisonment, and exile to win that right. You can bet that if he's being investigated, he's not going to be anywhere near as cooperative as he is advocating citizens should be. His advice is dangerous. And, he's using the trust some people put in police to get that dangerous message accepted.