Should I tell my nephew who has Asperger's he isn't entitled to everything just because he is a disorder?
That depends. What makes you think he feels entitled to everything?
I know he does. I can't accept his behavior any longer.
If your nephew has a disorder, you should try to understand his disorder. Telling him that he should not feel entitle because of it would make him feel bad and demonstrate your lack of understanding about his disorder.
So I should give up my rights to correct him because of his disorder.
No but there are better ways to correct improper behavior. You need to accept that he has a mental disability and because of that you need to do things differently than you would with a regular kid