I'm going to report my former autistic friend to the police for making passive aggressive threats against me on instagram
Why report someone to the police if they do not know any better?
People with autism spectrum disorders tends to respond well to therapies, but this is a serious case.
I think that it is wrong for them to make comments like that on social media. There is a better way to go about it though, you did not need to call the cops.  Why not talk to them in person?
Duh! I'm trying to show how autistic people are a threat to me on a social media.
You are right to not be threatened on social media, but you are wrong to get someone in trouble for something that could have been handled person to person.