My personal opinion is that you have these hypothetical numbers wrong. I think the proportion of voters who will vote for Trump in this election and "don't recognize what they're supporting" is a lot higher than you think because you are underestimating how uninformed and checked out these people are. There are millions of people who will cast a vote for Trump who don't support mass deportations. Millions who don't think we should try to fund the federal government with tariffs. Millions who are people of color and don't believe Trump is racist or that his campaign says racist things. Millions who have no idea what "Project 2025" is. These people will completely recoil at the notion that they are Nazis for voting for Trump. It will make them into the "unreachables" you say they already are. And it will turn off some of the people who are, insanely, still on the fence because it suggests they're Nazis for even thinking about Trump.
You call out the message from the Trump campaign, not the voters. We learned this, if nothing else, from Clinton. She called half of Trump's supporters "deplorable" and it turned into a full-blown political scandal that helped cost her the election; yet some people think it's a good idea to openly call every single Trump voter a Nazi, a much more negatively charged term? I fully support open and detailed explanations of why the Trump campaign is engaging in fascist rhetoric and what the dangers of going down that path are. I very much agree that there is no middle ground on fascism. But you have to frame that in a way that makes clear the fault is with the people pushing the message, not the voters who are potentially being swayed by it. Whether you think those voters are culpable or not. There is a reason the Trump campaign tries to turn every fascism accusation into an argument that "all Republicans/Trump voters are fascist" (the exact same thing they do with accusations of racism). it's because they know many of the more moderate voters who lean Republican will recoil at the idea that they're fascists, racists, Nazis, whatever. As I said, I very much agree from a moral standpoint that the people who vote to support this BS are culpable. But we are trying to win an election here, not a moral argument. You can't shame someone into voting for Kamala by telling them that if they don't, it makes them a Nazi sympathizer or Nazi enabler. Even if you believe that's true. It's the difference between being right and being persuasive.