You are the one who put it in their phone/inbox in the first place. You can argue about copyright laws or NDAs, but otherwise "private conversation" means nothing.

One-party recordings are illegal in many states. Just because I unicast some information something does not always give you the right to retain a record of it.

Recording laws are for phone calls. How would you even apply them to emails or texts?

Then you better go protest at Google's offices, because Gmail allows apps to interact with your email too.

by using Gmail, you are allowing Google to scrape what might otherwise be private messages

Indeed, and I am going to stop using Gmail as a result of this thread.

not sure if you're being sarcastic, but you really should. Everyone should. It will cost about $5/mo [fastmail] to make it happen, unfortunately most people don't seem to assign much value to privacy.