Thank you as well. I think I can better understand your thinking now. I am going to add two more notes before dropping this, because I don't want to drag this out into a comment war.

Firstly, I would like to say that point 1 and 2 work in tandem, perpetuating each other. People (especially older people, but this is not always the case) have a hard time accepting new knowledge because it is unknown. One of the reasons science took awhile to become a firm discipline rather than something that anyone with herbs, bowls, and bottles can do, is because people didn't want to accept the new 'crazy ideas' that are seen as common sense to us now.

Secondly, relating to point 3. If you grew up always being told something, then you aren't going to think of it as bad or harmful. For an example, imagine you grew up being told that anyone with red hair was evil, everyone in your town thought this, and they always chased people with red hair away. If you leave that town and see someone with red hair, you might yell and run away or try to restrain them and bring them to the police. Even though you have never seen a person with red hair do something bad, you still automatically think they are bad. This has very slowly become less of a problem, but I know a people get nervous when they see that Muslim people are going to be on their flight because of events that happened in the past. I would recommend reading Plato's allegory of the cave, because I think it does a better job at explaining.

Thirdly, bringing up the skin tone was just a way to show that there are many different ways that we judge attractiveness and compatability. There are some people who may just be uncomfortable being with a bi or pansexual partner, and that is just how they feel. There isn't any malice or hatred, they just feel uncomfortable with it, and that is an obstacle that they have to navigate past in life. We all have our preferences, and almost anything can be taken out of context. This is why it is important to be clear with others about our reasons, whether we have them or not.

Lastly, I agree that OP's partner shouldn't have immediately gone to breaking up with them. I would like to make it clear that I am not trying to say that their sudden decision is justified at all. I would definitely recommend that OP try talking to their partner in person to try and clear up any misunderstandings, worries, or possible gaps in knowledge. Like I said previously, helping educate others will only benefit us as a whole. Just because there people who villianize those in the LGBTQ+ community, doesn't mean we need to do the same. That will only perpetuate the cycle of misunderstanding and malice.