this will potentially be a self-defense case. since the shooter had chronic back pain, he could argue that shooting the ceo who denied his healthcare was his only means of protecting himself
That's not how criminal trials work. There are no free speech rights in court. Defendants can't just argue whatever they want. Judges have wide latitude to prohibit certain defenses and generally ban both the prosecution and defense from mentioning legally irrelevant points. Self defense is clearly codified under NY state law and this case doesn't even come close to meeting that standard.