Speaking as an autistic person, I think that there's a lot of misinformation out there that needs to be dealt with. Autism exists as a spectrum, and as best I can tell, most of us are higher functioning and it's the smaller number who are totally unable to function.
People also are woefully uneducated as to exactly what autism is. Bad portrayals in media are a big part of that I expect, but there's also just not a lot of education around. Autism is extremely hard to grasp and understand because it is hugely complex. There's a common misconception that autistic people are cognitively impaired, which is usually not the case at all. Then there's things that people just don't know, like how autistic people generally experience greater sensory input and what we do experience can be unusual, which is why we're often uncomfortable with certain kinds of contact or are pickier eaters than most. Then there's the belief that some have that we lack emotions when in reality autistic people tend to be highly emotional and instead struggle to communicate what we feel.
Most of what autistic people need to see change in society just stems from education. We need to be portrayed better and more accurately in media and information about autism (and other disabilities too for that matter) needs to be made more readily available.
If we want people to stop using "autistic" as an insult or to stop assuming we have below-average intelligence or any number of other things, we need to better educate those around us.
