I have no idea if this is what the OP is referring to, but it's pretty much impossible to use HTTPS on your home network without managing your own Root CA and somehow managing to get certificates signed by that Root CA into your devices.
You've got a fighting chance in a corporate network where you can deploy and manage the Root CA via Active Directory/Group Policy, but managing it at home with consumer-grade devices... not gonna be a good day.
I'm not sure what the original commenter meant; however TLS is useful only when talking with your own server. What about other connections? NTP, DNS etc are all unencrypted (read: unsigned). Google "DNS client CVE" for instance. Or what about SSH? It may not be accessible from the Internet, but still exploitable from an infected host in the LAN. Someone has to keep all that software updated.
In those conditions, I would never connect a RaspberryPI or similar to my door / gate / car / ...
If you connected an IoT device in the same network of an infected PC, the infected PC can talk to the IoT device directly if you do not block traffic somehow (eg. a firewall). Are there open ports with buggy services? Probably not today, what about in ten years?
I assume they mean you can only ssh from your local network, the IoT device gets pwnd, it's on the same network as the rest of your computers, someone can use the IoT device as an entry point into your network.
Easily solved with separate networks or vlans etc...
No no no. I am stating that, while TLS is good, your device will use other unprotected connections too (both on LAN and WAN) unless something else is done.
until bugs or weaknesses are found, see SSL v1/2/3 deprecation, heartbleed, etc
