"Will be used against you" to me is one of the strongest arguments against government surveillance without warrants. You can choose to not talk to police. You can't choose to have your data not gathered by the NSA.

You may be thinking of Don't Talk to the Police[1]? I'm not sure if the speaker explicitly says this or just quotes someone who did, but let's just say that this is a recurring theme in the talk...

[1] https://www.youtube.com/watch?v=d-7o9xYp7eE

Point 1 doesn't logically follow from the Miranda rights. In fact, that's the whole point of the adversarial court system: everything you say will be used for and against you, by the defense and the prosecution respectively.

How do you think your defense would obtain a copy of anything you said to use in your favor? In a situation where you would need it, it won't be presented unless you happen to have been recording yourself. But if you trust the police to not use things you say against you then you're also likely to trust them enough to not be recording your interactions.

The prosecution has no incentive or motivation to present evidence that could be used to the benefit of the defense.

>How do you think your defense would obtain a copy of anything you said to use in your favor?

https://en.wikipedia.org/wiki/Discovery_(law)

Specifically:

>Under the rule set forth in Brady v. Maryland, the prosecutor is obligated to provide to the defendant any information that is exculpatory or potentially exculpatory, without any request by the defense. Further discovery is available if initiated by the defendant. For example, a discovery demand might be for production of the names of witnesses, witness statements, information about evidence, a request for opportunity to inspect tangible evidence, and for any reports prepared by expert witnesses who will testify at trial.

You have far more faith in the system than I do and especially that the police wouldn't deny the existence of evidence that you said what you say you said if it suited them. Things are conveniently lost, misfiled or "never existed" in the first place.. They withold your statement from discovery. You claim they have a written report of your statement and knowingly withheld it. They claim they don't have it, have never had one, and it's nowhere to be found. Now what?