Depends on people, but for most it's mainly because Stallman says so.
You still have ethics ground if you think it the same way as repairability, actively blocking ways to repairs things you bought yourself is questionable, and keeping things closed source can be seen as a way to artificially prolonge a strict dependance on your vendor by impairing your ability to resolve issues by yourself.
Not disclosing the ingredients is illegal large part of the world, and people can die if you don’t do that, so the answer is clearly yes in some sense. This is also true for some cooking techniques, like heat treatment of raw meat. I think your analogy is not the best.
Not disclosing ingredients is more like not disclosing dependencies because I am very confident that you can't go into a shop, buy a random food and then construct recipe from list of ingredients.
It does however play a hugely important role in a recipe, in a way than the choice of language doesn't play in a program (especially considering turing completeness). So the analogy is broken.
Besides nobody made the point that list of ingredients makes a recipe.
Just that it's important to know the list of ingredients for a food you're gonna eat, and that it's even illegal to not disclose them (either to the public or a regulatory body) if you sell food.
As someone who also believes closed source software is unethical (though full of nuance), I don't appreciate the abrasive and combative (and frankly rude) way you are engaging on this. You're so epitomizing the rabid stereotype that part of me thinks you are just trolling and don't actually believe what you are saying.
If you actually care about this, stop alienating potential allies, and ideally start making arguments to support your case instead of telling people to RTFM (which in this case is even worse because "the manual" isn't as much of an authoritative mic drop as you seem to think it is).
This is the first paragraph after the initial quote defining "free software".
> We campaign for these freedoms because everyone deserves them. With these freedoms, the users (both individually and collectively) control the program and what it does for them. When users don't control the program, we call it a “nonfree” or “proprietary” program. The nonfree program controls the users, and the developer controls the program; this makes the program an instrument of unjust power.
It seems safe to say the author thinks that one creating "an instrument of unjust power" for oneself is unethical. Though, perhaps if the commenter in question pulled that quote out of the article, it could have helped their point.
You still have ethics ground if you think it the same way as repairability, actively blocking ways to repairs things you bought yourself is questionable, and keeping things closed source can be seen as a way to artificially prolonge a strict dependance on your vendor by impairing your ability to resolve issues by yourself.