Do you think it was wrong that I told my friend he's a high functioning autistic.
Is your friend really autistic?
No, I just wanted to be mean to him.
If your friend isn't really autistic you shouldn't say that they are. Leave this kind of diagnosis to people who are qualified to make it.
I saw it this morning on the internet.
A diagnosis like this really takes a professional in person assessment. You shouldn't try to diagnose someone based on information that you find on the internet.