Your argument is different to, and stronger than the parent's though. The parent's argument was not that we were on the thin end of a wedge to a totalitarian state, but that in some senses we had already passed that point because there was a voluntary element to it.
Still though, IR cameras by their nature are always-on and always transmitting data. They'd be pretty useless if they weren't! That's not the case for Google Home or any of the solutions currently on the market. Google Home also no-more violates this condition than say, a set top TV box that sends data on my TV viewing back to a central server.
If the public expects that a home might be recording their speech and sending it to a 3rd party - and thus theoretically has the opportunity to not speak or employ some sort of defense being recorded - then then Kyllo v United States suggests 4th Amendment protection no longer applies.
Just look at how many people here on HN already claim to no longer expect privacy.
> voluntary element
That's my point - your choice to voluntarily normalize surveillance impacts my 4th Amendment protections.
In the case of near-IR night vision CCTV cameras in common use, yes. The case of Kyllo v. United States specifically involved very expensive long-wavelength thermal imagers that are not typically used in civilian CCTV applications [0]. Furthermore, federal agents specifically pointed a mobile camera at the house to see temperature changes behind the walls, which differs from a static always-on installation.
[0] There are fixed thermal surveillance imagers (see http://www.flir.com/surveillance/display/?id=64664 for FLIR's latest), but they're typically used for military installation security. Unlike NIR cameras they require no external illumination, and are tuned to detect the black-body radiation naturally emitted by warm-blooded things.
> Law enforcement must have a valid and legal warrant
Kyllo v United States established a bright line test that the need for a warrant specifically depends on if the technology used is commonly available to and used by the general public.
At some point it is impossible to know the list of possible words you cannot speak and the public will simply start assuming that they may be recorded anyway. When that perception changes, so will legal doctrines.
You can own every single smarthome device in existence today and quite rightly assume that you are not being passively recorded. These concerns amount to overblown FUD.
One particularly interesting example of this Kyllo v United States[1], where the use of infrared cameras to find grow lights inside a home was ruled a search (and thus needed a warrant) because infrared cameras were not common so the general public did not in practice see infrared emissions as "available to the public". The opinion of the court, however, did point out that their decision would be defunct when infrared cameras became generally available and used by the public. At that point the public would no longer expect infrared emissions to be private. (Presumably this expectation might create a market for e.g. ir-blocking paint? If that's even possible?)
Installing microphones that regularly send data to unknown 3rd parties normalizes the expectation that spoken word in the home is no longer private. When perceptions change, so will warrant requirements.
> We're not living in a violent, single-party totalitarian regime.
If that's you're criteria for when to act, you are always going to be too late to do anything. Some of us prefer the idea of detecting problems early - hopefully before the become violent.
[1] https://en.wikipedia.org/wiki/Kyllo_v._United_States