I think some of the commenters are missing the point here. I don’t think the argument is whether a non-responsive aircraft entering an ADIZ shouldn’t be intercepted. To me, the question is why weren’t they communicating? Was it something out of their control (radio failure, failed handoff, etc), or was it more like that Northwest airliner a number of years ago in the US that flew past their destination because they were both distracted by a discussion they were having?
Also, a guilty plea doesn’t necessarily mean that they agree they were at fault - often people wil plea guilty out of expediency (e.g. they can’t afford a prolonged legal fight, or the prosecution offers a plea deal significantly lighter than they would persue in court).