Uh, uno reverse. You have missed understood the entire conversation.
[1] It starts of with rayiner saying that pornography isn't covered by the 1st amendment.
[2] To which I counter with, pornography isn't listed in the 1st amendment because the people who wrote it considered it a non-issue in the sense of "why wouldn't it be allowed?" since there was already nude imagery and prostitution.
[3] To which rayiner focused on that there are many pornography bans in the united states. While also bringing up the 4th amendment and saying it doesn't cover privacy.
[4] To which I counter with, as intended by the framers they would absolutely disagree with our current interpretation of the 4th and 5th amendments. They would agree that the 4th amendment restricts what you can take during a seizure to _just_ the items listed in the warrant. They would also agree that the 5th amendment restricts what you can use in court and somebody's personal belongings are restricted. So Stanley v Georgia would've still be a win for Stanley.
[5] To which rayiner claims (without evidence) that neither of those interpretations are correct.
[6] To which I counter with (with evidence), the 4th amendment is in response to seizures of belongings _not listed_ in the general warrant and the 5th amendment was previously cited in court as a reason that production of your personal belongings could be considered self-incrimination.
And that brings us to the present time with your post so lets quickly dissect that.
> which is that it has always been the law in the US
It has not always been the law. This is covered by [4] and [6] where originally you can only seize whats listed in the warrant. The interpretation has been changed for the expedience of prosecution but because it's interpretation was changed that means it wasn't "always the law".
> By the same principle, if they stop you for speeding or having an expired license tag and it is obvious that you are drunk or high, the fact that they didn't know (or couldn't have known) you were drunk or high when they decided to stop you does not prevent the authorities from using the evidence gathering during the traffic stop to convict you of driving under the influence.
This is an example involving neither the 1st, 4th, 5th, a warrant, or pornography so it's really not relevant to the discussion. However, if during the seizure of your vehicle (for it's misuse) the police found a gambling ledger that would run afoul of the 4th amendment and it's admittance in court would run afoul of the 5th amendment according to the original meaning.
[1]: https://news.ycombinator.com/item?id=40246109
[2]: https://news.ycombinator.com/item?id=40246440
[3]: https://news.ycombinator.com/item?id=40246804
[4]: https://news.ycombinator.com/item?id=40247108
[5]: https://news.ycombinator.com/item?id=40247591
[6]: https://news.ycombinator.com/item?id=40249433