Can't argue with that; it's hard to do, but it works. I had a client apprehended at the border who was seeking asylum and told her not to say anything ujnless I or another lawyer (I was working with a group representing undocumented persons at the time) was present. This is not easy, especally as she was in custody for over a month and moved around--from Texas to Chicago to New Orleans to Atlanta, and back to Chicago (personally, I think, to confuse us as to where she was and disorient her, but it is legal), but she held tough and was eventually released after her initial hearing (which I attended remotely), Speaking up wouldn't have helped her at all, and it rarely helps when apprehended and arrested by the police.
But what happened to taking the Fifth? Is that driving with an open container? In some traditions the proper response is not STFU, but Please Sir, may I have another? And how does STFU protect you from civil forfeiture? Me, I would prefer the cops beat me than be the victim of civil forfeiture. I don't think my car even has a right to counsel.
STFU is taking the fifth. And, you are correct, it does not protect you from civil forfeiture--not much does. and you could be both beaten and then the victim of a civil forfeiture--although you could prevent yourself from being the vicitim of a civil forfeiture by always driving someone else's car. You may lose a friend, but they'll lose the car.