My six year daughter is asperger (or would be if that were still distinct) and frankly her behavior is not just disruptive but absolutely horrible - she tantrums, bites and hurts anyone around her when she can't properly communicate her current "need" - and that need may be something completely unreasonable like ordering that the Santa at the mall be immediately removed from her vacinity.
Not all behaviors of autistic children - or adults - is ok and to be be cherished as a "difference". There are some behaviors that are fine - obsessions about dinosaurs, say, but there are many more that must be addressed before the child enters society. Smearing yourself with poo is NOT one of those differences that should be embraced.
Sorry, ranty after an afternoon having the shit kicked out of me because I wouldn't forward the Harry Potter audiobook to the correct precise instant she wants.