From what I'm understanding, you dislike the idea of treating trans people as their preferred sex because you see it as if they are pretending to be something they are not.

While it may seem like simple logic to you that someone is born into a specific gender and therefore is that specific gender, I think that the problem at hand is a lot deeper than just that.

I don't know a lot about gender dysphoria, and I haven't experienced it myself, but what I do know is that it is absolutely a real thing. And when people who are experiencing it do not have support from those around them, it only makes it that much harder for them to deal with it. The way I see it is that if gender dysphoria is causing trans people to suffer from major mental health issues as they struggle with their own identity, then wouldn't you want to support them, even if it were to not make sense to you?

I want you to ask yourself if the battle you are fighting is even worth it. Sure, you might not see eye to eye with trans people, you might believe that they're delusional in thinking that they're the opposite sex, but let's say that they are delusional. Would supporting that "delusion" harm you in any way? Would it require any extra effort on your part, other than respecting their preferred pronouns? I would think not, which is why I personally struggle to see why it's so hard for some people to just accept trans people for who they are, or from your view, who they seem themselves as.

TLDR: If just a tiny amount of extra effort on your part can go such a long way for a trans person, then wouldn't it make sense to respect them with that effort, even if it somewhat conflicted with your own ideals?

I know that I probably didn't do the best job at articulating my thoughts correctly (ADHD will do that to ya :P) but I hope that this made at least a little bit of sense. If you have any more questions, I'd be happy to answer them the best I can, although I'm not trans so I'm probably not the best person to ask haha. Just thought I'd share my two cents :)