Why does that make the statement "non-senscial"? Is it not factually accurate that the FISC doesn't hear opposing arguments?

>Granting warrants isn't an adversarial process in any U.S. court, neither are similar things like grand jury subpoenas.

The distinguishing factor is that normal court decisions and the outcome of grand jury proceedings are generally published for review by the public. If the court is too consistently siding with the government as a result of inherent bias in the process then people can get upset about it and try to change the law to modify the circumstances under which that can happen. A secret one-sided proceeding is legitimately different in character because it has yet one fewer safeguard against abuses of power, which makes the lack of opposing arguments more significant than it is when the outcomes are public.

It's non-sensical in the way it would be non-sensical of me to complain that the new Macbook Air doesn't have any 3.5" drive bays. Factually true, but how do you think people would react if they saw that in the Ars Technica review?

What I'm saying is that your analogy is off. The fact that the FISC only hears from one side is distinguishable from other courts because it's all kept secret. If a district court judge issues a bad warrant, that fact eventually comes out when marshals show up at the defendant's property to execute it or the evidence gained through it is presented in court. Then the defendant can challenge it in a public proceeding or, in sufficiently outrageous cases, the public can demand changes to the law or impeachment of the issuing judge.

There is none of that with the FISC. If the court makes a bad ruling, nobody is ever officially supposed to know, the government just starts hoovering up the data of American citizens under cover of darkness and anybody who brings this to the attention of the voting public will be accused of treason and then have their passport revoked and be stranded in a Russian airport.