Thanks for your answer, you raise some good questions.
Disclaimer: I’m probably going to get quite passionate with my answers. Please don’t mistake my passion for aggression, dislike or anything like that.
I think the main difference between nationality and gender is that there are other labels than Dutch available to you and you could have your nationality changed in your passport if you wanted to. It’s not easy and the other country has to accept you, but it’s possible. If you’d rather not like to have any specific country there but e.g. officially be a EU citizen instead I think that is a wonderful idea and you should fight for that. Ideally there should be an option not to have any nationality too, but unfortunately that won’t be an option for a long time I fear and will/would be a much harder (global political) fight.
For gender there are only two options available out of an infinite spectrum.
One reason why I think it’s worth to fight for individual labels for gender is that if the law acknowledges that something exists, the citizens will learn about it, at some point realize that it’s not something out of the norm, start to accept it and stop discriminating.
Also your examples - nerd and Dutch - are labels that are based on something about you, but were given to you by someone else. Labels you give yourself are different. If e.g. there was a label for eating habits in my passport with only the options carnivore and vegetarian available in my passport and I’d have to show it in every restaurant to get food based on it I’d fight for the option to have a vegan label too. That’s actually quite similar to what’s going on in some US states with the bathroom bills.
Well that’s easy: Because it concerns me directly. I’m happy to fight for things that don’t concern me directly. For example here in Austria we will probably be one of the last countries flooded when the sea levels rise, we are not (yet) directly affected by war and even our ultra-nationalist government doesn’t affect me personally, but still I do my part to fight climate change, war and nationalism. But of course fighting for something that concerns you is different. You automatically have some kind of expertise in the field (I have concrete ideas on how to fight gender-based discrimination, but I don’t have any specific ideas on how to end the Gaza-conflict. I only have a general simplistic idea on how to stop all conflicts: illegalize weapon manufacturing!).
I’m not sure I understand you here, but I’ll try to give an answer anyway. I don’t think linking identity to any label is ever bad. Someone who identifies hard with their nationality is not a nationalist. A nationalist is someone who discriminates others based on their nationality.
I recently thought about the word pride. I didn’t like it for a long time, but now I get it. There are two forms of pride: One based on thinking that you are better than others (e.g. nationalist, sexist,…) one based on simply being sick of being ashamed of who you are.
While I feel external shame (we call it fremdschämen) for austrian nationalists I feel proud e.g. of intersex people many of who have been through the worst (doctor ordered genital mutilation) and fight for other people’s rights not to have to go through the same in the future.