I’m not going to try to change your mind here. Changing someone’s mind means taking care to massage their emotions, make them feel good about themselves and you, and get them to make the decisions on their own for their own reasons. It’s a lot of work. I’m going to skip it.

Have you considered that you might be stupid? I’m not joking. Seriously. Because “I haven’t personally seen it, so I don’t think it’s real” in this kind of context, maybe most contexts, is weapons grade stupid. What else don’t you believe in? Bacteria? France? Submarines?

When you’re done being mad about being insulted, https://en.wikipedia.org/wiki/Violence_against_transgender_people might be a good entry point.