Who is to say that attacks might come from outside? Nations might mandate a backdoor from the Neuralink developers directly. Malevolent ones will surely want a literal kill switch feature, or copy the technology with their own. Imagine the horrifying power of a nation state that can kill any citizen at any time in any place with a keystroke. With that everpresent threat, you might not even need to be served propaganda to fall in line with the whims of the government.