Getting an Apple Private Key for signing the binary is also just a few blackmails and a gag order away. The average Apple engineer sure doesn't like to end up in jail for a prolonged time just because they happened to "find" some illegal material on one of his computers.
The sad truth is, the frameworks for something like this are already in place. There are "elements" in the government which have total control and surveillance at the very top of their agenda.
Controlling the media is easy (see Chinese, Russian State Televion etc.) but you also need to control the Internet these days. China is already really "good" at this and the US is also doing the groundwork, it's not as easy for them as it is for the Chinese, because they don't want to kill their tech sector and the billions of revenue for good overnight, so they have do introduce these things more slowly.
This is one of those cases where the betrayal of the NSA/GCHQ/Spy-Agencies-of-the-5-eyes-nations is really obvious. We can no longer trust our developer tools...
Last time I've checked apple was an US company. https://en.wikipedia.org/wiki/Patriot_Act
>If you distrust all software that isn't open source
Sadly, this isn't enough. A lot of people are pushing for deterministic builds for exactly this reason.