To what extent are Holocaust deniers doing so because of subconscious programming causing them to hold this view?

These individuals are very much victims of manipulation in exactly this fashion. It serves the Extraterrestrial Alliance to sow doubt and discord both. They care not who thinks what, about a particular issue. If there are bones of contention, it stirs up trouble, creates tension, and increases divisions among people who hold strong opinions on the matter at hand and will react, often quite strongly, to opposing views. When they have a particular campaign they believe has lots of mileage, so to speak, for causing trouble, they will spend quite a lot of time priming individuals to have differing points of view, depending on their preconceived notions, and this exploitation can be counted on to result in quite a lot of consternation and bad blood building up among many people following an argument or a competition to win hearts and minds on the part of advocates for a cause. This indeed is why such a notion can be embraced in spite of mountains of evidence of its reality and the belief will be rock-solid and unwavering regardless of what evidence to the contrary is offered and brought to the person’s attention. Once programmed in this way, they will simply not be able to engage with the evidence itself and give it any weight within their mind. They will simply tune it out. There will be no reaching them. This will be written off as prejudice or obstinacy when, in fact, it is actually an impairment of thinking restricted to the particular ideas in question—a blind spot, if you will—and is quite effective in creating legions of supporters or antagonists, or both, around a topic that need not be controversial but becomes so with opponents and supporters having been generated in this way. This has been done again, and again, and again across all fields of human endeavor whether at the academic level, within the media, within organizations and groups, and even with interpersonal relationships among couples and families when the stakes warrant this to be done. There is much subliminal programming designed for just this kind of implanting of points of friction and the carryover and consequences will be felt by millions of people as a consequence.