Perhaps an even closer analogy is not of a characteristic such as nationality or skin colour, but one of an ideological belief that inherently includes an offensive precept about an entire class of people?
So, bigotry to assume the one person you met from Tanzania has any bearing on any other people from Tanzania - this is prejudice, literally prejudging a person based upon a physical or material characteristic, making the false assumption that because they belong to a group who share characteristic A, they must also share negative trait B because you once met another person of that characteristic who had both.
However it doesn't follow with professed belief. If I meet one white supremacist, and I understand their professed beliefs, I can reject their position and find it appalling. I can extrapolate that to every white supremacist once I understand the precepts of this belief. I don't need to meet every white supremacist individually to check if they too are appalling or perhaps a jolly good chap. Their publicly professed beliefs tell me in advance that they already hold distasteful opinions. I'm not prejudiced, (literally pre-judging without facts) or judging them before I know the truth. Their professed belief as a self-declared white supremacist allows me the judgement based upon what those declared beliefs are already known to be.
I've purposely chosen an example where it's self-evident that a group holds unpleasant beliefs (the name gives it away). But there are other beliefs and belief groups that hold unpleasant ideals as a core principle of being in that group. And these are not always as transparent to others, until they dig deeper.
'Trans' is an ideological belief about the nature of men and women. One which I reject as firmly as I reject the idea that one 'race' is superior, or that wives should submit to husbands. I find the very principles it rests upon to allow a person to believe anyone can 'be trans' are sexist. Offensive beliefs come in all shapes, severities and sizes, some are obviously insidious and others not immediately so.
I think once a person has concluded that they reject the entire foundational belief that male people can be 'female inside', it's fair to understand that they will judge every person who holds that offensive belief similarly.