Comment by mjr00
Of course this is true. But you can keep going down the rabbit hole. How do you know there isn't a backdoor hidden in the source code? How do you know there isn't a compromised dependency, maybe intentionally?
Ultimately there needs to be trust at some point because nobody is realistically going to do a detailed security analysis of the source code of everything they install. We do this all the time as software developers; why do I trust that `pip install SQLAlchemy==2.0.45` isn't going to install a cryptominer on my system? It's certainly not because I've inspected the source code, it's because there's a web of trust in the ecosystem (well-known package, lots of downloads, if there were malware someone would have likely noticed before me).
> still running a random binary
Again "random" here is untrue, there's nothing random about it. You're running a binary which is published by the maintainers of some software. You're deciding how much you trust those maintainers (and their binary publishing processes, and whoever is hosting their binary).
The problem is that on Windows or your typical Linux distro "how much you trust" needs to be "with full access to all of the information on my computer, including any online accounts I access through that computer". This is very much unlike Android, for example, where all apps are sandboxed by default.
That's a pretty high bar, I don't blame your friend at all for being skeptical.