Interestingly, and not surprisingly coming from The Left, he is advocating capital punishment for possessing a philosophy rather than committing an act. Looking at history, that appears to be a constant.
That said philosophy is supported by, and adheres to, centuries of documented, established rights, which in turn is supported by the natural laws of this particular planet, is irrelevant to him; it is the philosophy he considers so dangerous.
This is certainly a real stretch – for the moment, anyway – but at what level does such a threat constitute basis for justifiable defensive action? For now it’s just talk; I suspect as political power waxes and wanes it may not always be.
I consider defensive training, stocking up on ammo, and keeping my home location difficult to find “defensive action” and more than justified by the current enumerable threats to my philosophy, person, and family. If you are talking about using deadly force as the “justifiable defensive action” then the answer is when the threat is eminent and of a nature that it would result in death or permanent injury to an innocent person.
Other than that I have nothing to add.—Joe]