To be fair most don't even know what it is. Ignorance and stupidity lead to harm. Not to excuse the lack acceptance but understanding it's source is how we can defeat it.
This partly because the science isn't quite there yet. We've come a long way in our understanding but still have far to go I think. unfortunately the general public isn't patient, if the science isn't well established they just seem to ignore it.
There's also still a lack of accessibility for assements and resources. In Canada it took me over 2 years to get my assessment and the process was terribly unorganized. I was told I'd get some free classes on "so your are autistic, now what" but that never came and our provincial primire made huge cuts to our programs (genuinely hate that guy).
This isn't to excuse the "others" but for empathy many of them may be part of our group and not know it.
It's tough but it's on us to reach out to those around us and try to explain things. Pave the way for the autistic folk of the future.
Not to excuse the lack acceptance but understanding it's source is how we can defeat it.
To be clear, I hope you mean defeating the lack of widespread understanding and care for autistics, not "defeating autism", whatever that would entail. I like the way my brain works, and I hope you like yours. The problem is other people being assholes to us.
For now advocating for some years and meeting numerous autists, it's the sad truth for autistics too. Autists don't know what autism is. Therapists are doing a bad work at explaining and many parents hide the fact their kids are autistic. These people can't empower themselves on a lifetime basis without having the right support.
The first step is to deconstruct what people told them and define autism again or for some, or define autism for the first time, both in an non medical model and in accordance with the neurodiversity paradigm. After defining, you can begin the work of empowerment on this basis.