Knowing that, you should realize that a disassembler is just one or two of those steps reversed, the "assembler" steps, which should make if pretty much self-explanatory.
And I'm talking about looking at a 20 byte function; you could figure it out if you wanted.
[1] I don't use Ubuntu so maybe it doesn't fully apply here. On Arch using pacman, the list of mirrors/caches is mostly commented out so that people can choose their own. They are "trustworthy" essentially until they're not, but we have signature checking to fall back on. In the physical world we don't have this, thus the setup of my (again, flawed) analogy.
Any more involved than that and it's missing the spirit of what I was trying to say, but I admit that the disassembler response made me chuckle.
The point is that you're using 'binary blob' to sound scarier than it is. With a statue there's no reason to fear it (for reasons explained in other posts). With an image displayer an expert can poke it and then announce there's no reason to fear it.
You're telling me I should be ready to wipe my disks then and there, even though it's just an image displayer, but that's an overreaction. Your analogy just strengthens the point that the park shouldn't panic.
Have to laugh at this, because only on HN is the use of a disassembler considered "easy."
True story, I program computers for a living, and I have literally no idea how to verify anything at all with a disassembler. Or even approximately how one works.