But in this case it wasnt the Cessna that screwed up. It followed all the rules it had to follow.
He's dead so clearly he didn't do enough. Why is that so freaking hard to understand, that the minimum required rules compliance is not enough if you want to live very long in the aviation world? I'd be dead 10 times over if I only ever did what the minimum rules required, and I've saved at least 5 aircraft by going beyond the minimum requirements.
I repeat - he's dead, so he clearly didn't do enough. Legal doesn't mean safe, compliance doesn't mean a mistake or error or natural occurrence won't sneak up on you and kill the unwary or lazy pilot.
That viper driver could have been squawking 1200 (or 4000) and legally not talking to anyone either, and they'd still have collided, both complying with their minimum obligation under the rules. Just because something is legal or rules-compliant doesn't mean it is effective or safe.
That's why the FAA has the "see and avoid" rules in place, because when it comes down to it you can easily die or collide with an object, another plane, the ground, etc, with 100% compliance, meeting every obligation except the obligation to preserve your life and the lives of those in your aircraft. The PIC is responsible for safe execution of the flight, and that goes well beyond simple rules compliance.
The cropduster who flew VFR without a transponder through Sheppard AFB's high training volume transit corridor was compliant. He's dead. The T-37 that he collided with was also 100% compliant. The ATC controllers who were providing VFR advisory services to the T-37 were fully compliant. Compliance with the bare minimum requirements and obligations left 2 pilots descending in their parachutes and a cropduster pilot who didn't value his life enough to have a working transponder or 2-way radio comm with Sheppard controllers probably died screaming since he augered in from about 7,000 ft.
I could give a poop about minimum compliance... Lots of dead people out there who were fully rules-compliant and thought that was enough. Idiots. Not my fault they didn't value their lives enough to truly comply with the one rule that actually mattered, the one about the PIC being the sole person responsible for the safe execution of the flight from takeoff to landing.