;-)
It's important to keep orthogonal issues separate so you don't cross contaminate and introduce unintended outcomes.
Well, you set up a straw man, so the rules of logic had already been implicitly suspended in that branch of the conversation.
> the same questions apply on searches for guns, stolen property or any other contraband
No, they don't. Dogs can't generally sniff out guns or distinguish between stolen and non-stolen property, and so dogs can't be used as a pretense in those situations. Using a dog to sniff out stolen property (unless that stolen property happens to be a salami) would make it obvious that the dog is just a pretense.
> It's important to keep orthogonal issues separate
Indeed.
So let's review: the problem is that although dogs can sniff out drugs, unless some very strict protocols are followed, they generally don't sniff out drugs and instead just tell their handler what they want to hear, i.e. that there are drugs (though, of course, the dog has no idea that this is how its actions are being interpreted. All it knows is that if it signals, it gets a pat on the head.)
As a result, dogs are not an effective crime fighting tool, but instead a de facto pretense for doing an end-run around the fourth amendment. The same effect could be produced by other means, e.g. flipping a biased coin, but that would defeat the purpose because that would make the bias obvious, which is exactly the rhetorical point that the original author wanted to make.
Do you really want to disagree with any of that?