I am really low on energy today and so can't write as much as I'd like to, but did want to comment and at least say you're not alone.
I, too, am a Christian and generally don't mention it online due to the criticism that usually follows. A combination of conflicts (at least one of which was exacerbated by my autism) and the response to the COVID-19 pandemic and the politics that followed completely undermined my faith in the church as an institution; I have not attended church in several years. Suffering autistic burnout makes that worse since that significantly exacerbates all the sensory issues too. Sadly it is Christians (at least in my experience) that tend to have the poorest understanding of mental health and neurodivergent conditions such as ASD.
The majority of being stigmatized/being made to feel like I didn't belong was during my childhood and teen years. These days I am well-versed at masking (which is a separate problem) and so don't attract negative attention in the same way anymore (though I still don't feel like I fit in in a lot of places). I have slowly educated my family as I have learnt more about autism over the past couple of decades and whilst some of the extended family are still difficult to deal with, my immediate family has a much, much better handle on it these days and occasionally even surprises me with their level of awareness.
As for friends and acquaintances, I no longer have the time or energy to deal with people who can't at least make an effort to see where I'm coming from, ASD or not. This year has seen me realise I need to cut a few more people out of my life, as they are not good for me and my mental health.